drm/drm_internal.h: Remove repeated struct declaration

struct drm_gem_object is declared twice. One is declared
at 40th line. The blew one is not needed. Remove the duplicate.
Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210401081704.1000863-1-wanjiabing@vivo.com

drivers/gpu/drm/drm_internal.h

@@ -170,7 +170,6 @@ void drm_sysfs_connector_remove(struct drm_connector *connector);
 void drm_sysfs_lease_event(struct drm_device *dev);
 
 /* drm_gem.c */
-struct drm_gem_object;
 int drm_gem_init(struct drm_device *dev);
 int drm_gem_handle_create_tail(struct drm_file *file_priv,
 			       struct drm_gem_object *obj,