ASoC: cs48l32: Use modern PM_OPS

When building for a platform that does not support CONFIG_PM, such as
s390, cs48l32_runtime_{suspend,resume}() are unused because
SET_RUNTIME_PM_OPS does not reference its argument when CONFIG_PM is not
set:

sound/soc/codecs/cs48l32.c:3822:12: error: 'cs48l32_runtime_suspend' defined but not used [-Werror=unused-function]
3822 | static int cs48l32_runtime_suspend(struct device *dev)
| ^~~~~~~~~~~~~~~~~~~~~~~
sound/soc/codecs/cs48l32.c:3779:12: error: 'cs48l32_runtime_resume' defined but not used [-Werror=unused-function]
3779 | static int cs48l32_runtime_resume(struct device *dev)
| ^~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

Use RUNTIME_PM_OPS and pm_ptr() to ensure these functions are seen as
used by the compiler but be dropped in the final object file when
CONFIG_PM is not set, matching the current behavior while clearing up
the warnings.

Fixes: e2bcbf99d045 ("ASoC: cs48l32: Add driver for Cirrus Logic CS48L32 audio DSP")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://patch.msgid.link/20250418-cs48l32-modern-pm_ops-v1-1-640559407619@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>