ASoC: rcar: Convert to SYSTEM_SLEEP_PM_OPS()

ASoC: rcar: Convert to SYSTEM_SLEEP_PM_OPS()

Use the newer SYSTEM_SLEEP_PM_OPS() macro instead of
SET_SYSTEM_SLEEP_PM_OPS() together with pm_ptr(), which allows us to
drop ugly __maybe_unused attributes.

This optimizes slightly when CONFIG_PM is disabled, too.

Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://patch.msgid.link/20250317095603.20073-75-tiwai@suse.de
Signed-off-by: Mark Brown <broonie@kernel.org>