ASoC: adau1373: Remove unnecessary suspend/resume bias level changes

The ASoC core will only call the suspend/resume callbacks when the device's
DAPM context is idle. Since this driver sets idle_bias_off to true this
means that the device is already in SND_SOC_BIAS_OFF when the suspend
callback is called, so there is no need to manually set this state again.
There is also no need to go to SND_SOC_BIAS_STANDBY in the resume callback
since the core will go right back to SND_SOC_BIAS_OFF.

Also drop the regcache_cache_only() calls from the suspend and resume
handlers. There shouldn't be any IO happening after suspend and before
resume.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@kernel.org>