drm: Fixup kernel doc for driver->gem_create_object

Silences

./include/drm/drm_drv.h:295: warning: Incorrect use of kernel-doc format
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161125123427.15188-1-chris@chris-wilson.co.uk

include/drm/drm_drv.h

@@ -291,6 +291,8 @@ struct drm_driver {
 	void (*gem_close_object) (struct drm_gem_object *, struct drm_file *);
 
 	/**
+	 * @gem_create_object: constructor for gem objects
+	 *
 	 * Hook for allocating the GEM object struct, for use by core
 	 * helpers.
 	 */