The controller has mute/unmute capability and some bootloader may mute
them at boot. If it's not handled, all things will seem to be working
but no sound will come out of the speaker/headphone.
Signed-off-by: Arnaud Patard <arnaud.patard@rtp-net.org> Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>