drm: remove transient drm_gem_object_put_unlocked()

As of last commit, all the drivers have been updated away from the
_unlocked helper. As such we can now remove the transient #define.

v2: keep sed and #define removal separate

Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org> (v1)
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20200515095118.2743122-39-emil.l.velikov@gmail.com

include/drm/drm_gem.h

@@ -375,8 +375,6 @@ drm_gem_object_put(struct drm_gem_object *obj)
 	kref_put(&obj->refcount, drm_gem_object_free);
 }
 
-#define drm_gem_object_put_unlocked drm_gem_object_put
-
 void drm_gem_object_put_locked(struct drm_gem_object *obj);
 
 int drm_gem_handle_create(struct drm_file *file_priv,