ASoC: SOF: Intel: Add legacy IPC support

Add IPC support required for devices introduced before Skylake
(Merrifield, baytrail, CherryTrail, Haswell, Broadwell)

Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@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>