drm/msm: Fix another leak in the submit error path

[ Upstream commit f681c2aa ]

put_unused_fd() doesn't free the installed file, if we've already done
fd_install().  So we need to also free the sync_file.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Patchwork: https://patchwork.freedesktop.org/patch/653583/


Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>