ASoC: Intel: sof_sdw: use single rtd_init for rt_amps

ASoC: Intel: sof_sdw: use single rtd_init for rt_amps

2 amps can be in the same or different dai links. To handle this, the
existing code implements different spk_init functions to add dapm routes
for different amps. However, sof_sdw.c doesn't support non-aggregated
amp any more since it used pre-defined BE id.
With that assumption, combine the spk_init functions together.
This is a preparation of putting different types amps in a single dai
link.

Reviewed-by: Rander Wang <rander.wang@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://lore.kernel.org/r/20240208165545.93811-10-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>