msm: mdss: prevent dereferencing of user space pointer

We were dereferencing a userspace pointer in kernel.

Change-Id: I128455904cd396690350fc6b784a8844d594539c
Signed-off-by: Terence Hampson <thampson@codeaurora.org>

Conflicts:
	drivers/video/msm/mdss/mdp3_ctrl.c