msm: vidc: Initialize kernel space stack variables

This change initializes kernel space stack variables
that are passed between kernel space and user space
using ioctls.
Non initialization of these variables may lead to
leakage of memory values from the kernel stack to
user space.
Change-Id: Icb195470545ee48b55671ac09798610178e833e1
CRs-fixed: 556771,563420
Signed-off-by: Deepak Verma <dverma@codeaurora.org>