ASoC: imx-audmux: Switch to SYSTEM_SLEEP_PM_OPS

ASoC: imx-audmux: Switch to SYSTEM_SLEEP_PM_OPS

Replace SET_SYSTEM_SLEEP_PM_OPS() with its modern SYSTEM_SLEEP_PM_OPS()
alternative.

The combined usage of pm_sleep_ptr() and SYSTEM_SLEEP_PM_OPS() allows
the compiler to evaluate if the suspend/resume() functions
are used at build time or are simply dead code.

This allows removing the CONFIG_PM_SLEEP ifdefery from the
suspend/resume() functions.

Signed-off-by: Fabio Estevam <festevam@denx.de>
Link: https://patch.msgid.link/20240808184944.267686-6-festevam@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>