drm/vc4: Handing the return value of drm_universal_plane_init

Handing the return value of drm_universal_plane_init to fix the following
W=1 kernel build warning(s):
vc4_plane.c: In function ‘vc4_plane_init’:
vc4_plane.c:1340:6: warning: variable ‘ret’ set but not
used [-Wunused-but-set-variable]
Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/1599811777-34093-1-git-send-email-tiantao6@hisilicon.com

drivers/gpu/drm/vc4/vc4_plane.c

@@ -1361,6 +1361,8 @@ struct drm_plane *vc4_plane_init(struct drm_device *dev,
 				       &vc4_plane_funcs,
 				       formats, ARRAY_SIZE(formats),
 				       modifiers, type, NULL);
+	if (ret)
+		return ERR_PTR(ret);
 
 	drm_plane_helper_add(plane, &vc4_plane_helper_funcs);