ASoC: SOF: Intel: hda: Add a virtual CPU DAI

ASoC: SOF: Intel: hda: Add a virtual CPU DAI

Add a virtual CPU DAI for loopback capture for echo reference
implementation. We can't use the snd-soc-dummy-dai because it is already
used for the bluetooth DAI link.

Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Liam Girdwood <liam.r.girdwood@intel.com>
Reviewed-by: Mateusz Redzynia <mateuszx.redzynia@intel.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Link: https://patch.msgid.link/20260204081833.16630-11-peter.ujfalusi@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>