fbdev: msm: Signal fences in legacy display commit path

For targets where the display ATOMIC_COMMIT ioctl is not used,
the commit_cnt was not getting incremented during display
commits. Due to this, release/retire fences were not signalled
resulting in UI freeze. Fix this by incrementing commit_cnt in
pan_display_ex path and use 'timeline_retire' for retire fences.

Change-Id: Ief016d949a4aa9f6b7d4fa11d1031e693a463621
Signed-off-by: Nirmal Abraham <nabrah@codeaurora.org>