ASoC: Intel: sof_sdw: remove unused rt dmic rtd_init

ASoC: Intel: sof_sdw: remove unused rt dmic rtd_init

Some Realtek SDW DMIC codecs use the generic rt_dmic_rtd_init callback now.
Remove unused rtd_init callbacks.

Reviewed-by: Chao Song <chao.song@linux.intel.com>
Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://msgid.link/r/20240326160429.13560-26-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>