msm: mdss: Add check for ioctl calls

A check is added to ensure that only the supported
ioctl calls are allowed to proceed further and
all other ioctl calls are returned early.

Change-Id: I30f69bc9c60384d01f990bd1830ddc1d8aa9241e
Signed-off-by: Krishna Manikandan <mkrishn@codeaurora.org>