ASoC: nau8821: new driver

The driver is for codec NAU88L21 of Nuvoton Technology Corporation.
The NAU88L21 is an ultra-low power high performance audio codec that
supports both analog and digital audio functions.

Signed-off-by: Seven Lee <wtli@nuvoton.com>
Link: https://lore.kernel.org/r/20211001103108.3297848-1-wtli@nuvoton.com


Signed-off-by: Mark Brown <broonie@kernel.org>