msm: vidc: Add control to configure latency hint

The control would hint the video driver to prepare
for latency mode during the video session.

CRs-Fixed: 2682236
Change-Id: Ied0307ff66b755005dcd4fe05189d7e864be208e
Signed-off-by: Vikash Garodia <vgarodia@codeaurora.org>