msm: mdss: compat: get/put retire fence fd in buf sync ioctl

copy retire fence fd in the buf sync structure as a part of
buf sync compat ioctl implementation. This fd is an essential
part of the buf sync implementation that needs to be included
in the compat layer.

Change-Id: If60b5f9115ccb128bc7b56a735b06c31fa0e47f6
Signed-off-by: Manoj Rao <manojraj@codeaurora.org>