ASoC: pcm: DRAIN support reactivation

soc-pcm's dpcm_fe_dai_do_trigger() supported DRAIN commnad up to kernel
v5.4 where explicit switch(cmd) has been introduced which takes into
account all SNDRV_PCM_TRIGGER_xxx but SNDRV_PCM_TRIGGER_DRAIN. Update
switch statement to reactive support for it.

As DRAIN is somewhat unique by lacking negative/stop counterpart, bring
behaviour of dpcm_fe_dai_do_trigger() for said command back to its
pre-v5.4 state by adding it to START/RESUME/PAUSE_RELEASE group.

Fixes: acbf2774 ("ASoC: pcm: update FE/BE trigger order based on the command")
Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Link: https://lore.kernel.org/r/20201026100129.8216-1-cezary.rojewski@intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/soc-pcm.c

@@ -2206,6 +2206,7 @@ static int dpcm_fe_dai_do_trigger(struct snd_pcm_substream *substream, int cmd)
 		case SNDRV_PCM_TRIGGER_START:
 		case SNDRV_PCM_TRIGGER_RESUME:
 		case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
+		case SNDRV_PCM_TRIGGER_DRAIN:
 			ret = dpcm_dai_trigger_fe_be(substream, cmd, true);
 			break;
 		case SNDRV_PCM_TRIGGER_STOP:
@@ -2223,6 +2224,7 @@ static int dpcm_fe_dai_do_trigger(struct snd_pcm_substream *substream, int cmd)
 		case SNDRV_PCM_TRIGGER_START:
 		case SNDRV_PCM_TRIGGER_RESUME:
 		case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
+		case SNDRV_PCM_TRIGGER_DRAIN:
 			ret = dpcm_dai_trigger_fe_be(substream, cmd, false);
 			break;
 		case SNDRV_PCM_TRIGGER_STOP: