ASoC: soc-pcm: add snd_soc_dai_get_pcm_stream()

DAI driver has playback/capture stream.
OTOH, we have SNDRV_PCM_STREAM_PLAYBACK/CAPTURE.
Because of this kind of implementation,
ALSA SoC needs to have many verbose code.

To solve this issue, this patch adds snd_soc_dai_get_pcm_stream() macro
to get playback/capture stream pointer from stream.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87ftf7jcab.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>