ANDROID: usb: gadget: f_audio_source: New gadget driver for audio output

This driver presents a standard USB audio class interface to the host
and an ALSA PCM device to userspace

Bug: 78114713
Bug: 120441124
[badhri: f_audio_source is being migrated to userspace.]
Change-Id: If16b14a5ff27045f9cb2daaf1ae9195c5eeab7d0
Signed-off-by: Mike Lockwood <lockwood@google.com>
[AmitP: Folded following android-4.9 commit changes into this patch
        Parts of e27543931009 ("ANDROID: usb: gadget: Fixes and hacks to make android usb gadget compile on 3.8")
        i6d9285e2574a ("ANDROID: usb: gadget: f_audio_source:replace deprecated API")]
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
[astrachan: Folded the following changes into this patch:
            ddfd0c4070c1 ("ANDROID: usb: gadget: f_audio_source: Move to USB_FUNCTION API")
            a3ab81aaa19e ("ANDROID: usb: gadget: f_audio_source: Move gadget functions code")
            2095c953d894 ("ANDROID: usb: gadget: f_audio_source: change max ISO packet size")
            8671b3e53638 ("ANDROID: usb: gadget: f_audio_source: Fixed USB Audio Class Interface Descriptor")
            af98f36edbe2 ("ANDROID: usb: gadget: f_audio_source: disable the CPU C-states upon playback")
            a830751a338e ("CHROMIUM: usb: gadget: f_audio_source: add .free_func callback")]
Signed-off-by: Alistair Strachan <astrachan@google.com>