drm/msm/sde: restrict directly accessing data in user pointers

Restrict directly dereferencing user pointers by casting with the
proper attribute.  Some properties accept a 64-bit value as a
pointer to a user space structure.  This data should only be
accessed after copying to the kernel address space.

Change-Id: I968dc92061263176f714d1fda5e75db3921dfc3e
Signed-off-by: Steve Cohen <cohens@codeaurora.org>