ASoC: max98520: add max98520 audio amplifier driver

add max98520 audio amplifier driver

Signed-off-by: George Song <george.song@maximintegrated.com>
Link: https://lore.kernel.org/r/20211027001431.363-2-george.song@maximintegrated.com
Signed-off-by: Mark Brown <broonie@kernel.org>