drm/udl: Make udl_handle_damage static

Fix the following sparse warning:

drivers/gpu/drm/udl/udl_modeset.c:269:5: warning: symbol 'udl_handle_damage'
was not declared. Should it be static?
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: NZou Wei <zou_wei@huawei.com>
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1588248797-70568-1-git-send-email-zou_wei@huawei.com

drivers/gpu/drm/udl/udl_modeset.c

@@ -266,8 +266,8 @@ static int udl_aligned_damage_clip(struct drm_rect *clip, int x, int y,
 	return 0;
 }
 
-int udl_handle_damage(struct drm_framebuffer *fb, int x, int y,
-		      int width, int height)
+static int udl_handle_damage(struct drm_framebuffer *fb, int x, int y,
+			     int width, int height)
 {
 	struct drm_device *dev = fb->dev;
 	struct dma_buf_attachment *import_attach = fb->obj[0]->import_attach;