ASoC: SOF: Add Nocodec machine driver support

Add a simple "fallback" machine driver that can be used to enable SOF
on boards with no codec device. This machine driver can also be forced
for debug/development.

Signed-off-by: Keyon Jie <yang.jie@linux.intel.com>
Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Mark Brown <broonie@kernel.org>