ASoC: rt-sdw-common: Common functions for Realtek soundwire driver

This is the first version of common functions for Realtek
soundwire codec driver.

Signed-off-by: Jack Yu <jack.yu@realtek.com>
Link: https://patch.msgid.link/959e8dcb075948459be4463f6a4ca6ee@realtek.com


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