drm/gem: remove bogus NULL check from drm_gem_object_handle_unreference_unlocked

Calling this function with a NULL object is simply a bug, so papering
over a NULL object not a good idea.
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_gem.c

@@ -238,9 +238,6 @@ static void drm_gem_object_handle_free(struct drm_gem_object *obj)
 void
 drm_gem_object_handle_unreference_unlocked(struct drm_gem_object *obj)
 {
-	if (obj == NULL)
-		return;
-
 	if (atomic_read(&obj->handle_count) == 0)
 		return;