drm/gem: make drm_gem_object_handle_unreference_unlocked static

No one outside of drm should use this, the official interfaces are
drm_gem_handle_create and drm_gem_handle_delete. The handle refcounting
is purely an implementation detail of gem.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index b8a8132..52548fd 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -231,7 +231,7 @@
 	}
 }
 
-void
+static void
 drm_gem_object_handle_unreference_unlocked(struct drm_gem_object *obj)
 {
 	if (WARN_ON(obj->handle_count == 0))