ASoC: ssm3515: Add new amp driver

The Analog Devices' SSM3515 is a mono audio amplifier with digital
input, equipped on Apple's 2021 iMacs. Add an ASoC driver for it, and
register both the driver code and schema in MAINTAINERS.

Signed-off-by: Martin Povišer <povik+lin@cutebit.org>
Link: https://lore.kernel.org/r/20230511150546.8499-3-povik+lin@cutebit.org


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