d2: USB audio support

 * Add required usecases for USB PROXY RX and TX.

Change-Id: Id3433188e557d8d9aedc1dd6d347460e0f7bb438
d2: Add "length" parameter for /data partition

 * Needed for "footer" style encryption.

Change-Id: I685354b5e7a44cfff19ee5bcedeb773bd26b8b1d
d2-common:  Fix Camcorder Audio

Under 10.2 we are using the Speaker DMIC Stereo settings not
Camcorder Tx.   This finally brings audio up to where we can
hear what was recorded.

Change-Id: Ibfc328534f2ce29ee1ed0a1d93d1fa4a31141ca2
expressatt bringup