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: If2ad6b9672081e94b52d17d969858abf8bd4c4dc
CRs-fixed: 556771,563420
Signed-off-by: Deepak Verma <dverma@codeaurora.org>