ASoC: SOF: ops: fallback to mmio in helpers

Returning an error when a read/write is not implemented makes no
sense, especially on read where no return value makes sense.

Change the logic to directly fallback to mmio. If a platform truly
wants other read/writes that are not plain vanilla mmio, it needs to
implement its own routines.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Link: https://lore.kernel.org/r/20221024165310.246183-2-pierre-louis.bossart@linux.intel.com


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