ASoC: rsnd: check whether playback/capture property exists

Current rsnd sets "channels_min" which is used from
snd_soc_dai_stream_valid() without checking DT playback/capture property.
Thus, "aplay -l" or "arecord -l" will indicate un-exising device.
This patch checks DT proerty and do nothing playback/capture settings if
not exist.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/878rhi6t7x.wl-kuninori.morimoto.gx@renesas.com


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