ASoC: mchp-pdmc: use runtime pm for clock power saving

Implement clock power saving taking advantage of runtime PM infrastructure.
This simplifies the code and allow using the same infrastructure for
suspend to RAM functionalities.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20221213112851.89212-3-claudiu.beznea@microchip.com


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