ASoC: Intel: add mutual exclusion between SOF and legacy Baytrail driver

This legacy driver is already deprecated, let's make sure there is no
conflict with SOF.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20191101173045.27099-4-pierre-louis.bossart@linux.intel.com


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