msm_fb: display: Add timeout for waiting on update

Content Adaptive BackLight userspace algo waits on UPDATE_NOTIFY to
get the screen updates. When turning off CABL, this blocking ioctl
causes the CABL threads to wait until next screen update, which may
take indefinite time.

Add timeout value to the wait_for_completion call, to make ioctl
call blocking for at most timeout value.

CRs-Fixed: 384026
Change-Id: I6715a36020c24ddd09823bd54d4321900429a6b9
Signed-off-by: Kinjal Bhavsar <kbhavsar@codeaurora.org>