msm: mdss: Install sync fences after user copy

If userspace closes the fd after an error on copying to
userspace, the fences may be freed incorrectly. Make sure fences
are installed after all checks pass.

Bug: 32402303
Change-Id: Ieb50296c87e09549db2734bd70bb6ee8d311ad40
CRs-Fixed: 2000664
Signed-off-by: Naseer Ahmed <naseer@codeaurora.org>