msm_fb : Check the validity of Histogram start/stop ioctls.

Histogram start/stop ioctls are called now without checking
if the panel is on or not. Add check to validate the ioctl
calls in this aspect.

CRs-fixed: 327910
Change-Id: Idc110408841c1b813dd2331a63cafe80243baeac
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>
2 files changed