drm/qxl: Do not cause spice-server to clean our objects

commit 2fa19535 upstream.

If objects are moved back from system memory to VRAM (and spice id
created again) memory is already initialized so we need to set flag
to not clear memory.
If you don't do it after a while using desktop many images turns to
black or transparents.
Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/gpu/drm/qxl/qxl_cmd.c

@@ -505,6 +505,7 @@ int qxl_hw_surface_alloc(struct qxl_device *qdev,
 
 	cmd = (struct qxl_surface_cmd *)qxl_release_map(qdev, release);
 	cmd->type = QXL_SURFACE_CMD_CREATE;
+	cmd->flags = QXL_SURF_FLAG_KEEP_DATA;
 	cmd->u.surface_create.format = surf->surf.format;
 	cmd->u.surface_create.width = surf->surf.width;
 	cmd->u.surface_create.height = surf->surf.height;