msm: camera: icp: use mutex to avoid sleep in spin_lock

__might_sleep() cannot be called inside spin_lock,
clock core has __might_sleep() call so use mutex
in place of spin_lock.

Change-Id: Ib09097fa4371a5105553af49f4c75643884cd892
Signed-off-by: Tejas Prajapati <tpraja@codeaurora.org>