msm: sde: update histogram buffer submission for ltm

When histogram buffer is queued by driver client, during the display
commit buffer has to be submitted to hardware. Currently driver is
waiting for previous histogram to finish before submitting the new
buffer. This can cause the histogram to be invalid, change updates the
submission logic of buffer.

Change-Id: I76b595fa96d1c2dd01c841de3cf228d4fa7fd75d
Signed-off-by: Gopikrishnaiah Anandan <agopik@codeaurora.org>