hikey: Enable usb audio support

It was noticed on the 96boards forum by user "niruyadla"
that USB audio support was missing, so this patch enables
it along with adding tinyplay for help w/ testing.

Also adds r_submix and tweaks audio policy to be consistent

Change-Id: Ia65468ddd2144b2cba3304fefcefbe01574ab772
Signed-off-by: John Stultz <john.stultz@linaro.org>
2 files changed