usb: android: f_uac2: Add support for UAC2 function

Integrate USB Audio class (UAC2) function driver with
android gadget. Unlike UAC1 driver, this exposes sound
card to allow playback/capture control from userspace.
While at it also fix issues related to composition
switch, and composite device enumeration that requires
updating bFirstIface for IAD descriptor

CRs-fixed: 1097689
Change-Id: I6ac8f3b5d9036a81bd2e82c558ff0f93090ce5a9
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>