msm-camera: Adding lock and unlock methods for

ISP subdev

Added lock mechanism to lock hardware update
when a sof is received, and ignore any other sof
which is received between the update process

Change-Id: If2013a566be0c45a48bf180aa6e16bd5f03cff3c
Signed-off-by: Megha Tak <mtak@codeaurora.org>