ui/gtk: skip refresh if new dmabuf has been submitted

ui/gtk: skip refresh if new dmabuf has been submitted

Skip refresh if a new dmabuf (guest scanout frame) has already been
submitted and ready to be drawn because the scanout will be updated
with new frame anyway.

Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Cc: Vivek Kasireddy <vivek.kasireddy@intel.com>
Signed-off-by: Dongwon Kim <dongwon.kim@intel.com>
Acked-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-ID: <20230706183355.29361-2-dongwon.kim@intel.com>