msm: mdss: Validate CSC ioctl for black screen in mdp3

If csc register data coming from ioctl has mv as all zeros
then a black screen is seen. This can be unrecoverable until
another csc ioctl with correct data arrives. Adding an
additional validation step to curb such spurious ioctl
data from getting programmed.

Change-Id: Id6355822a642720d80b98b7d4585a74758b3016f
Signed-off-by: Krishna Chaitanya Parimi <cparimi@codeaurora.org>