msm: camera: isp: Protect access to module_cfg register with lock

For vfe 40 and 44, frame modules and stats modules are enabled
by bits in same register. These are enabled from 2 different
contexts. Hence need to protect the access to this register with
lock to avoid race condition.

Change-Id: Ie066bb3317c26d2c62bcfb34cbf270d913b6205d
Signed-off-by: Harsh Shah <harshs@codeaurora.org>