ASoC: nau8315: add codec driver

Add codec driver for Nuvoton NAU8315.

Signed-off-by: David Lin <CTLIN0@nuvoton.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20201102023212.594137-1-CTLIN0@nuvoton.com


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