I9100G: Audio HAL updates from Tuna

Squashed commit of the following:

commit b6603126f69fbf4346363cb644fa7a8d769967b0
Author: Eric Laurent <elaurent@google.com>
Date:   Fri Jan 18 18:05:45 2013 -0800

    audio: added support for dual mic capture.

    Added support for simultaneous capture from front and back
    mics.

    Change-Id: Ica1b75fe432f419272ae92e8ab04b1d34524c189

commit 16681520c9f391a7f9bc74c4af01b65bee180945
Author: Eric Laurent <elaurent@google.com>
Date:   Thu Apr 04 09:27:52 2013 -0700

    audio: implement mute on hdmi multichannel

    On direct output streams the audio HAL must implement
    the volume function. In the case of HDMI the only function
    required is to mute audio when volume is 0 as volume
    is defined as fixed on digital output streams.

    Bug 8541062

    Change-Id: I4b4e28a910e7b321b3a68567e9ad03fede065ca8


Change-Id: I2a6b8f539752d5dd85ddb5a090573f577fe25cb4