ASoC: stm32: dfsdm: add pm_runtime support for audio

Enable support of pm_runtime on STM32 DFSDM audio driver
to allow power state monitoring.

Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
Link: https://lore.kernel.org/r/20211119104752.13564-3-olivier.moysan@foss.st.com


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