drm/atomic: Convert drm_atomic_get_private_obj_state() to use new plane state

The drm_atomic_get_private_obj_state() function tries to find if a
private_obj had already been allocated and was part of the given
drm_atomic_state. If one is found, it returns the existing state
pointer.

At the point in time where drm_atomic_get_private_obj_state() can be
called (ie, during atomic_check), the existing state is the new state
and we can thus replace the hand-crafted logic by a call to
drm_atomic_get_new_private_obj_state().

Reviewed-by: Ville Syrjälä <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Maxime Ripard <[e-mail]>

drivers/gpu/drm/drm_atomic.c

···
 drm_atomic_get_private_obj_state(struct drm_atomic_state *state,
 				 struct drm_private_obj *obj)
 {
-	int index, num_objs, i, ret;
+	int index, num_objs, ret;
 	size_t size;
 	struct __drm_private_objs_state *arr;
 	struct drm_private_state *obj_state;
 
-	for (i = 0; i < state->num_private_objs; i++)
-		if (obj == state->private_objs[i].ptr)
-			return state->private_objs[i].state;
+	obj_state = drm_atomic_get_new_private_obj_state(state, obj);
+	if (obj_state)
+		return obj_state;
 
 	ret = drm_modeset_lock(&obj->lock, state->acquire_ctx);
 	if (ret)