msm: vidc: Validate input data before processing

User controlled data needs to be validated before
processing, otherwise it may corrupt existing data
and other programming variables which may further
lead to crash in kernel space.
This change validates user specified buffer's data,
such as offset and data length, before performing
any operations in kernel.

Change-Id: Idb2a5c4c270cdbb55adfc0c22b9296b7dd359de9
CRs-fixed: 547695
Signed-off-by: Deepak Verma <dverma@codeaurora.org>
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>