post_proc: add support for virtualizer capability query

Add extra virtualizer interfaces to keep align with aosp design.
Extended capabilities include:
- Stub interface to allow querying speaker angles.
- Force set output device as specific virtualize mode.
- Query virtualize mode

Stub function remains to be refined in sync with upcoming aosp
changes.

Change-Id: I3316f6d944db1c9954eda7643a5ce433defa1a6c
CRs-Fixed: 810294