ASoC: Intel: sof_sdw: use playback/capture_only flags

Prepare for removal of dpcm_playback and dpcm_capture flags in
dailinks.

[Kuninori adjusted Pierre-Louis's patch]

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://patch.msgid.link/87o75maah5.wl-kuninori.morimoto.gx@renesas.com


Signed-off-by: Mark Brown <broonie@kernel.org>