ASoC: uniphier: add support for UniPhier AIO common driver

This patch adds common functions for UniPhier AIO audio sound
system. This provides commonly used APIs for input/output control
registers for UniPhier AIO.

This module provides all sound devices for I2S, S/PDIF and so on.
Since the AIO has mixed register map for those I/Os, it is hard
to split register areas for each sound devices.

Signed-off-by: Katsuhiro Suzuki <suzuki.katsuhiro@socionext.com>
Signed-off-by: Mark Brown <broonie@kernel.org>