ASoC: rt1318: Add RT1318 audio amplifier driver

This is the initial i2s-based amplifier driver for rt1318.

Signed-off-by: Jack Yu <jack.yu@realtek.com>
Link: https://msgid.link/r/b3055442ce6d4994aa01aa1fad6ba1fe@realtek.com


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