bcm2708: alsa sound driver

    Signed-off-by: popcornmix <popcornmix@gmail.com>

alsa: add mmap support and some cleanups to bcm2835 ALSA driver

snd-bcm2835: Add support for spdif/hdmi passthrough

This adds a dedicated subdevice which can be used for passthrough of non-audio
formats (ie encoded a52) through the hdmi audio link. In addition to this
driver extension an appropriate card config is required to make alsa-lib
support the AES parameters for this device.

snd-bcm2708: Add mutex, improve logging

Fix for ALSA driver crash

Avoids an issue when closing and opening vchiq where a message can arrive before service handle has been written

alsa: reduce severity of expected warning message

snd-bcm2708: Fix dmesg spam for non-error case