ASoC: Intel: sof_sdw: use common helpers for all Realtek amps

sof_sdw_rt1308.c/sof_sdw_rt1316.c/sof_sdw_rt1318.c handle amp
in basically the same way, optimized and merged into one file.

Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Signed-off-by: Gongjun Song <gongjun.song@intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20221206212507.359993-3-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>