ASoC: sunxi: Add new driver for Allwinner A64 codec's analog path controls

The internal codec on A64 is split into 2 parts. The analog path controls
are routed through an embedded custom register bus accessed through
the PRCM block.

Add an ASoC component driver for it. This should be tied to the codec
audio card as an auxiliary device.

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Mark Brown <broonie@kernel.org>