ASoC: codecs: ssm2305: Use dev_err_probe() helper

Use the dev_err_probe() helper, instead of open-coding the same
operation.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/20211214020843.2225831-10-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>

ASoC: ssm2305: fix header layout

Make C-header and SPDX-License-Identifier header uniform.

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Signed-off-by: Mark Brown <broonie@kernel.org>

ASoC: ssm2305: Add amplifier driver

The ssm2305 is a simple Class-D audio amplifier. A application can
turn on/off the device by a gpio. It's also possible to hardwire the
shutdown pin.

Tested on a i.MX6 based custom board.

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@kernel.org>