ASoC: Intel: sof_sdw: Add a DAI link for loopback capture

ASoC: Intel: sof_sdw: Add a DAI link for loopback capture

Add a DAI link for loopback capture as the last link to make sure
the other DAI link ID's remain unaffected. It serves as a dummy DAI link
to enable echo reference capture in the SDW topologies which do not have
an actual backend capture DAI.

Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Link: https://patch.msgid.link/20260204081833.16630-5-peter.ujfalusi@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>