drm: Fix kerneldoc for "Returns" section

The blank line between title "Returns:" and detail description is not
allowed, otherwise the title will goes under the description block in
generated .html file after running `make htmldocs`.

There are a few examples for current kerneldoc at [1][2][3].

v2:
- use Link tag with stable URLs

Signed-off-by: renjun wang <[e-mail]>
Link: https://www.kernel.org/doc/html/v6.10/gpu/drm-kms.html#c.drm_crtc_commit_wait # 1
Link: https://www.kernel.org/doc/html/v6.10/gpu/drm-kms.html#c.drm_atomic_get_crtc_state # 2
Link: https://www.kernel.org/doc/html/v6.10/gpu/i915.html#c.i915_vma_pin_fence # 3
Reviewed-by: Thomas Zimmermann <[e-mail]>
Signed-off-by: Thomas Zimmermann <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/display/drm_dp_mst_topology.c

···
  * drm_dp_atomic_release_time_slots()
  *
  * Returns:
- *
  * 0 if the new state is valid, negative error code otherwise.
  */
 int drm_dp_mst_atomic_check(struct drm_atomic_state *state)
···
  * topology object.
  *
  * RETURNS:
- *
  * The MST topology state or error pointer.
  */
 struct drm_dp_mst_topology_state *drm_atomic_get_mst_topology_state(struct drm_atomic_state *state,
···
  * topology object.
  *
  * Returns:
- *
  * The old MST topology state, or NULL if there's no topology state for this MST mgr
  * in the global atomic state
  */
···
  * topology object.
  *
  * Returns:
- *
  * The new MST topology state, or NULL if there's no topology state for this MST mgr
  * in the global atomic state
  */

drivers/gpu/drm/drm_atomic.c

···
  * hardware and flipped to.
  *
  * Returns:
- *
  * 0 on success, a negative error code otherwise.
  */
 int drm_crtc_commit_wait(struct drm_crtc_commit *commit)
···
  * not created by userspace through an IOCTL call.
  *
  * Returns:
- *
  * Either the allocated state or the error code encoded into the pointer. When
  * the error is EDEADLK then the w/w mutex code has detected a deadlock and the
  * entire atomic sequence must be restarted. All other errors are fatal.
···
  * is consistent.
  *
  * Returns:
- *
  * Either the allocated state or the error code encoded into the pointer. When
  * the error is EDEADLK then the w/w mutex code has detected a deadlock and the
  * entire atomic sequence must be restarted. All other errors are fatal.
···
  * object lock to make sure that the state is consistent.
  *
  * RETURNS:
- *
  * Either the allocated state or the error code encoded into a pointer.
  */
 struct drm_private_state *
···
  * make sure that the state is consistent.
  *
  * Returns:
- *
  * Either the allocated state or the error code encoded into the pointer. When
  * the error is EDEADLK then the w/w mutex code has detected a deadlock and the
  * entire atomic sequence must be restarted. All other errors are fatal.
···
  * state is consistent.
  *
  * Returns:
- *
  * Either the allocated state or the error code encoded into the pointer. When
  * the error is EDEADLK then the w/w mutex code has detected a deadlock and the
  * entire atomic sequence must be restarted.

drivers/gpu/drm/drm_atomic_helper.c

···
  * automatically.
  *
  * Returns:
- *
  * 0 on success. -EBUSY when userspace schedules nonblocking commits too fast,
  * -ENOMEM on allocation failures and -EINTR when a signal is pending.
  */
···
  * don't pass the right state structures to the callbacks.
  *
  * Returns:
- *
  * Returns 0 on success. Can return -ERESTARTSYS when @stall is true and the
  * waiting for the previous commits has been interrupted.
  */

drivers/gpu/drm/drm_file.c

···
  * resources for it. It also calls the &drm_driver.open driver callback.
  *
  * RETURNS:
- *
  * 0 on success or negative errno value on failure.
  */
 int drm_open(struct inode *inode, struct file *filp)
···
  * in-kernel DRM client.
  *
  * RETURNS:
- *
  * Always succeeds and returns 0.
  */
 int drm_release(struct inode *inode, struct file *filp)
···
  * then restores the active in-kernel DRM client.
  *
  * RETURNS:
- *
  * Always succeeds and returns 0.
  */
 int drm_release_noglobal(struct inode *inode, struct file *filp)
···
  * safety.
  *
  * RETURNS:
- *
  * Number of bytes read (always aligned to full events, and can be 0) or a
  * negative error code on failure.
  */
···
  * See also drm_read().
  *
  * RETURNS:
- *
  * Mask of POLL flags indicating the current status of the file.
  */
 __poll_t drm_poll(struct file *filp, struct poll_table_struct *wait)
···
  * already hold &drm_device.event_lock.
  *
  * RETURNS:
- *
  * 0 on success or a negative error code on failure.
  */
 int drm_event_reserve_init_locked(struct drm_device *dev,
···
  * drm_event_reserve_init_locked() instead.
  *
  * RETURNS:
- *
  * 0 on success or a negative error code on failure.
  */
 int drm_event_reserve_init(struct drm_device *dev,

drivers/gpu/drm/drm_gem.c

···
  * For a single handle lookup, use drm_gem_object_lookup().
  *
  * Returns:
- *
  * @objs filled in with GEM object pointers. Returned GEM objects need to be
  * released with drm_gem_object_put(). -ENOENT is returned on a lookup
  * failure. 0 is returned on success.
···
  * @filp: DRM file private date
  * @handle: userspace handle
  *
- * Returns:
+ * If looking up an array of handles, use drm_gem_objects_lookup().
  *
+ * Returns:
  * A reference to the object named by the handle if such exists on @filp, NULL
  * otherwise.
- *
- * If looking up an array of handles, use drm_gem_objects_lookup().
  */
 struct drm_gem_object *
 drm_gem_object_lookup(struct drm_file *filp, u32 handle)
···
  * @timeout: timeout value in jiffies or zero to return immediately
  *
  * Returns:
- *
  * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
  * greater than 0 on success.
  */

drivers/gpu/drm/drm_modes.c

···
  * to reach those resolutions.
  *
  * Returns:
- *
  * A pointer to the mode, allocated with drm_mode_create(). Returns NULL
  * on error.
  */

drivers/gpu/drm/drm_rect.c

···
  * factors from @src to @dst.
  *
  * RETURNS:
- *
  * %true if rectangle @dst is still visible after being clipped,
  * %false otherwise.
  */

drivers/gpu/drm/drm_vblank.c

···
  * drm_atomic_helper_calc_timestamping_constants().
  *
  * Returns:
- *
  * Returns true on success, and false on failure, i.e. when no accurate
  * timestamp could be acquired.
  */
···
  * drm_atomic_helper_calc_timestamping_constants().
  *
  * Returns:
- *
  * Returns true on success, and false on failure, i.e. when no accurate
  * timestamp could be acquired.
  */

drivers/gpu/drm/i915/gem/i915_gem_object.h

···
  * @handle: userspace handle
  *
  * Returns:
- *
  * A pointer to the object named by the handle if such exists on @filp, NULL
  * otherwise. This object is only valid whilst under the RCU read lock, and
  * note carefully the object may be in the process of being destroyed.

drivers/gpu/drm/i915/gt/intel_ggtt_fencing.c

···
  * For an untiled surface, this removes any existing fence.
  *
  * Returns:
- *
  * 0 on success, negative error code on failure.
  */
 int i915_vma_pin_fence(struct i915_vma *vma)

drivers/gpu/drm/i915/i915_vma.h

···
  * i915_vma_unpin_fence().
  *
  * Returns:
- *
  * True if the vma has a fence, false otherwise.
  */
 int __must_check i915_vma_pin_fence(struct i915_vma *vma);