msm: rotator: Wait for the pending commits in finish IOCTL

Due to asynchronuous rotator mechanism, sometimes the
MSM_ROTATOR_IOCTL_FINISH arrives before the previously queued
do_rotate work is completed. This causes fence to be signalled
before the buffer is used by rotator. In case of fast YUV 2 pass
scenario, this causes IOMMU page fault on 2 pass buffers, since
the buffer is unmapped when the rotator is still using it. Hence,
wait for the pending commit works to be finished before releasing
the fence and freeing the 2 pass buffers.

Change-Id: Iec9edd11406d102c7dd102c2ad7935184bbbba93
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>
Signed-off-by: Naseer Ahmed <naseer@codeaurora.org>