drm/i915/gem: fix function pointer member kernel-doc

You can't document function pointer member as functions.

drivers/gpu/drm/i915/gem/i915_gem_region.h:25: warning: Incorrect use of kernel-doc format: * process_obj - Process the current object
drivers/gpu/drm/i915/gem/i915_gem_region.h:35: warning: Function parameter or member 'process_obj' not described in 'i915_gem_apply_to_region_ops'

Signed-off-by: Jani Nikula <[e-mail]>
Reviewed-by: Rodrigo Vivi <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/a2a[e-mail]

drivers/gpu/drm/i915/gem/i915_gem_region.h

···
  */
 struct i915_gem_apply_to_region_ops {
 	/**
-	 * process_obj - Process the current object
-	 * @apply: Embed this for private data.
-	 * @obj: The current object.
+	 * @process_obj: Process the current object
 	 *
 	 * Note that if this function is part of a ww transaction, and
 	 * if returns -EDEADLK for one of the objects, it may be