Adding ability to specify stereo-type in pvx.

Currently, only left/right stereo can be specified in pvx since other types
cause multiple renders that need to be synced up across all processes.

Change-Id: Ic87c5f9c5b2e5d60626742de00d5a9f8dd9497b9
Merge topic 'add_stereo_type_to_pvx' into next

f430aa6 Adding ability to specify stereo-type in pvx.