drivers: usb: gadget: Add uac1 legacy audio driver

This is a snapshot of uac1 audio driver from msm-3.18 at
'commit 8c4dd1c9dfcc ("Promotion of kernel.lnx.3.18-170213.")'
Port uac1 legacy function driver to support speaker, micro
phone and fix code styling.

Change-Id: I3802dc2fa70a1a0507bc4797504f3bf3977385ba
Signed-off-by: Sudharsan Reddy Yettapu <syepattu@codeaurora.org>
Signed-off-by: Sivasri Kumar Vanka <sivasri@codeaurora.org>