In the specific case where the display layer (virtio-gpu) is using
dmabuf, and if remote clients are enabled (-spice gl=on,port=xxxx),
it makes sense to limit the maximum (streaming) rate to 60 FPS
using the GUI timer. This matches the behavior of GTK UI where the
display updates are submitted at 60 FPS (assuming the underlying
mode is WxY@60).

Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Cc: Frediano Ziglio <freddy77@gmail.com>
Cc: Dongwon Kim <dongwon.kim@intel.com>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>