ASoC: fsl_spdif: Add pm runtime function

Add pm runtime support and move clock handling there.
Close the clocks at suspend to reduce the power consumption.

fsl_spdif_suspend is replaced by pm_runtime_force_suspend.
fsl_spdif_resume is replaced by pm_runtime_force_resume.

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Acked-by: Nicolin Chen <nicoleotsuka@gmail.com>
Link: https://lore.kernel.org/r/579c0d71e976f34f23f40daa9f1aa06c4baca2f1.1592552389.git.shengjiu.wang@nxp.com


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