drm/ast: Unpin cursor BO during cleanup

The unpin operation was missing from ast_cursor_fini(). Fixed now.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190613073041.29350-3-tzimmermann@suse.de

drivers/gpu/drm/ast/ast_mode.c

@@ -959,6 +959,7 @@ static void ast_cursor_fini(struct drm_device *dev)
 	struct drm_gem_vram_object *gbo =
 		drm_gem_vram_of_gem(ast->cursor_cache);
 	drm_gem_vram_kunmap_at(gbo, &ast->cache_kmap);
+	drm_gem_vram_unpin(gbo);
 	drm_gem_object_put_unlocked(ast->cursor_cache);
 }