hal: Support the audio amplifier hook

* Original legacy HAL commit:
  Ib236598a5888b2af19bcfb81e285f644a0e84c0d
* Example: http://review.cyanogenmod.org/38221

 (cyanogen: Refactored to be an audio_extn)

Change-Id: Ic944a9f7059c78b79322dae9c787cdd8bb029cff

audio: add amplifier stream start/standby operations

Change-Id: I5de7ad7a0467e7cf822c9c0870a755c03d05e884

hal: Convert libaudioamp to audio_amplifier HAL

Change-Id: I1d0f63a46989d1792d7a5e08d2bdb6344ebafa31

hal: Notify amplifier of device enable/disable

Change-Id: Ice808c9b55a9e3bc8bafe5ca3ff555377d38dd8f

hal: enable amplifier earlier

Change-Id: Id876e8f836e3ce1ee5f8186ca9c0e6ef5f37182c

hal: only open the amplifier once

Change-Id: Ie9bbff74123e90b71e95809a84dcb3bbe9ba82fe

hal: notify amplifier of parameter changes

Change-Id: Iecc020c0347ae7c43d27183186e06dcefef7a0dd

hal: Clean up audio amplifier usage

 * Externalize it into an extension file similar to the rest.

Change-Id: I03de7efa9bab8870099028170fa471dfffe1ce84

hal: switch audio_extn_set_parameters and amplifier_set_parameters

Switch set_param calls so amplifier_set_parameters can be used
to set ANC parameter. audio_extn_set_parameters will pick it up
and refresh device selection for anc playback.

Change-Id: I4fda3f9a76db14a20af2c8c7be8c90a63a5f1153