msm: mdss: fb: Copy & send unsigned value for notify update

Copy unsigned long from userspace and modify the data fields
before copying back unsigned long data to userspace. This
keeps the datatypes of all operands homogeneous without
data leaks from kernel to user land.

CRs-Fixed: 526286
Change-Id: Ie4673563170c3459019dd6a5f1f55376f6e560c7
Signed-off-by: Krishna Chaitanya Parimi <cparimi@codeaurora.org>
Signed-off-by: Manoj Rao <manojraj@codeaurora.org>