fbdev: msm: Avoid duplicate release fence fd creation

The mdss release fence fd was getting created twice during
buf_sync_ioctl call. This was leading to fence fd leak.
Fix this by removing extra call to mdss_get_sync_fence_fd.

Change-Id: I24b646d3de7246b8483eefbadd9da7293e593c09
Signed-off-by: Nirmal Abraham <nabrah@codeaurora.org>