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>
msm: vidc: Check validity of userspace address

Before writing to a userspace address, verification
of the validity of user space address is required.

Change-Id: I9141e44a6c11aaf3f4d57c08bb0dd26a7b214f34
CRs-fixed: 556356
Signed-off-by: Deepak Verma <dverma@codeaurora.org>
msm: vidc: Validate userspace buffer count

Makesure the number of buffers count is less than
the maximum limit to avoid structure overflow errors.

Change-Id: Icf3850de36325637ae43ac95f1c8f0f63e201d31
CRs-fixed: 563694
Signed-off-by: Pachika, Vikas Reddy <vpachi@codeaurora.org>