msm: vidc: Fix update of actual buffer count to firmware

Video driver should check client set actual count against
firmware requested min count before setting the actual
count to firmware. Without this change, if client sets
an initial higher buffer count and then sets a lower buffer
count, the latter count does not get set to firmware.

Change-Id: I2c986b4fc880cca2cc6d2698b33b549100eae988
Signed-off-by: Arun Menon <avmenon@codeaurora.org>