msm: fb: Null check mfd data

Add appropriate null check for mfd data
structure before accessing it's members.
This prevents null pointer accesses in
the driver.

Change-Id: I5aae937f839e4f6ed8d5c5a4b54ab45f0ff07332
Signed-off-by: Krishna Chaitanya Parimi <cparimi@codeaurora.org>
msm: fb: Copy unsigned int for notify update

Change to correct signature of msmfb_notify_update
from the ioctl declaration.

Change-Id: Ia7bdfd3dbe8494a641ffd46d484794b4bec7d27c
Signed-off-by: Krishna Chaitanya Parimi <cparimi@codeaurora.org>