[media] media-entity.h: remove redundant macro definition for gobj_to_pad()

The macro gobj_to_pad() is defined twice in media-entity.h.
Let's remove one.
Signed-off-by: Liu Ying <gnuiyl@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

include/media/media-entity.h

@@ -520,9 +520,6 @@ static inline bool media_entity_enum_intersects(
 #define gobj_to_link(gobj) \
 		container_of(gobj, struct media_link, graph_obj)
 
-#define gobj_to_pad(gobj) \
-		container_of(gobj, struct media_pad, graph_obj)
-
 #define gobj_to_intf(gobj) \
 		container_of(gobj, struct media_interface, graph_obj)