msm: mdss: Make wait_for_complete calls uninterruptible

The wait_for_complete calls in the MDSS driver are associated
with an acceptable timeout value which would remove the need for
making them interruptible. Also, this prevents unwanted signal
interrupts before the call is finished.

Change-Id: If4013b0d74bc9f717c4a63d961f2a34753320e87
Signed-off-by: Sree Sesha Aravind Vadrevu <svadrevu@codeaurora.org>