msm: VPU: Add tunneling support for VPU video post-processing unit

This change is required for tunneling mode in VPU.
VPU handles input buffers from VCAP and sends the output
buffers to display in tunneling mode.

Change-Id: Iceb49b1991bdb5ca6bbc26047ca25aa0de52effe
Signed-off-by: Stephane Viau <sviau@codeaurora.org>
Signed-off-by: Mohammed Sardar <msardar@codeaurora.org>