hal: Adding Pan-Scale, downmix mixer control support.

Add support in HAL to send mix matrix params using downmix,
Pan-Scale mixer controls. Add new interactive usecases and
also add support to open and teardown for interactive streams.
Add support in test app for supporting up to 9 concurrent
streams. Add support for mixer matrix params handling.

Change-Id: I0dc5b908ee779b2b2c526a67609c057f591f26e7