msm: camera: isp: Avoid cuncurrency between CRM operations

Camera context layer works on state machine principle that
allows events to drive state transition and operation based
on current state. Taking mutex_lock while processing the events
and operations will avoid any conflict because of scheduling
and state transitions.

Change-Id: I6042bb9bf6cb3b6eb1c2dcb6646cf0b353623971
Signed-off-by: Abhilash Kumar <krabhi@codeaurora.org>