DO NOT MERGE - audio: audio HAL extension for routing and volume control

DO NOT MERGE - audio: audio HAL extension for routing and volume control

Added audio HAL functions to control audio routing and audio gain.
Audio HALs above version 3.0 must implement these functions.
These functions will be used by the framework instead of
out_set_parameters("routing"=XXX) for device selection on an output
or input stream.
They will also allow direct connection of input devices to output devices
as well as gain control on devices or streams.

The gain or routing capabilities are exposed in audio_polciy.conf file.

Change-Id: Ic293fd41d492e38e86bdc35e3ad93aa5deb0b48f