ASoC: stm32: i2s: add pm_runtime support

Enable support of pm_runtime on STM32 I2S driver to allow
I2S power state monitoring.

Signed-off-by: Olivier Moysan <olivier.moysan@foss.st.com>
Link: https://lore.kernel.org/r/20211119104752.13564-2-olivier.moysan@foss.st.com


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