drm: update crtc x/y when only fb changes

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
index ff447f1..fe86974 100644
--- a/drivers/gpu/drm/drm_crtc_helper.c
+++ b/drivers/gpu/drm/drm_crtc_helper.c
@@ -869,6 +869,9 @@
 		}
 		drm_helper_disable_unused_functions(dev);
 	} else if (fb_changed) {
+		set->crtc->x = set->x;
+		set->crtc->y = set->y;
+
 		old_fb = set->crtc->fb;
 		if (set->crtc->fb != set->fb)
 			set->crtc->fb = set->fb;