ASoC: Intel: add SNDRV_PCM_INFO_DRAIN_TRIGGER flag

Add SNDRV_PCM_INFO_DRAIN_TRIGGER in snd_pcm_hardware.info to
call sst_hsw_stream_set_silence_start() when PCM draining.
Signed-off-by: Libin Yang <libin.yang@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/soc/intel/sst-haswell-pcm.c

@@ -91,7 +91,8 @@ static const struct snd_pcm_hardware hsw_pcm_hardware = {
 				  SNDRV_PCM_INFO_INTERLEAVED |
 				  SNDRV_PCM_INFO_PAUSE |
 				  SNDRV_PCM_INFO_RESUME |
-				  SNDRV_PCM_INFO_NO_PERIOD_WAKEUP,
+				  SNDRV_PCM_INFO_NO_PERIOD_WAKEUP |
+				  SNDRV_PCM_INFO_DRAIN_TRIGGER,
 	.formats		= SNDRV_PCM_FMTBIT_S16_LE | SNDRV_PCM_FMTBIT_S24_LE |
 				  SNDRV_PCM_FMTBIT_S32_LE,
 	.period_bytes_min	= PAGE_SIZE,