ASoC: soc-pcm: dpcm: fix playback/capture checks

ASoC: soc-pcm: dpcm: fix playback/capture checks

Recent changes in the ASoC core prevent multi-cpu BE dailinks from
being used. DPCM does support multi-cpu DAIs for BE Dailinks, but not
for FE.

Handle the FE checks first, and make sure all DAIs support the same
capabilities within the same dailink.

Fixes: f27f69de3f74ae ("ASoC: soc-pcm: dpcm: Only allow playback/capture if supported")
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Daniel Baluta <daniel.baluta@gmail.com>
BugLink: https://github.com/thesofproject/linux/issues/2031
Link: https://lore.kernel.org/r/20200608194415.4663-2-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>