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 before using it

Validate the number of buffers count variable before
using it to avoid structure overflow error.

Change-Id: I61582c93e0f26ec6842e437134fb8a42bdbc36ff
CRs-fixed: 563654
Signed-off-by: Pachika, Vikas Reddy <vpachi@codeaurora.org>