msm: vidc: Add support for batching input and output frames to Venus

Setting the control V4L2_CID_VIDC_QBUF_MODE allows the client to mark
frames to be held back via V4L2_MSM_BUF_FLAG_DEFER.  The end of a batch
on a specific capability is signalled by the lack of a DEFER flag, at
which point the driver might submit the frames to the hardware for
processing.  In keeping Venus operational only in bursts, the hope is
that the system uses less overall power by increasing the time that H/W
sleeps and reducing the number of wakeups due to interrupts.

Change-Id: I6a589b2d419911548fcd03ee241194c50b95ec82
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>