ASoC: ak5558: Add regulator support

"AVDD" is for analog power supply,  "DVDD" is for digital power
supply, they can improve the power management.

As the regulator is enabled in pm runtime resume, which is
behind the component driver probe, so accessing registers in
component driver probe will fail. Fix this issue by enabling
regcache_cache_only after pm_runtime_enable.

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Link: https://lore.kernel.org/r/1598190877-9213-2-git-send-email-shengjiu.wang@nxp.com


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