xwayland: don't use GBM_BO_USE_SCANOUT

This flag should only be used when the caller intends to display the
buffer on a hardware plane. Xwayland isn't a DRM client, so it doesn't
make sense to use this flag.

This change will allow the driver to potentially use buffer parameters
that are more optimized.

Signed-off-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>

hw/xwayland/xwayland-glamor-gbm.c

@@ -239,7 +239,7 @@ xwl_glamor_gbm_create_pixmap(ScreenPtr screen,
 #endif
         {
             bo = gbm_bo_create(xwl_gbm->gbm, width, height, format,
-                               GBM_BO_USE_SCANOUT | GBM_BO_USE_RENDERING);
+                               GBM_BO_USE_RENDERING);
         }
 
         if (bo) {