ALSA: mips: Use SNDRV_PCM_INFO_SYNC_APPLPTR info flag

The recently introduced PCM info flag assures the call of ack ops at
each applptr change, and this is mandatory for the indirect PCM
helpers.

Also, with the proper ack callback, we need no longer prefill at
trigger start.  The relevant code can be killed.
Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/mips/hal2.c

@@ -500,7 +500,8 @@ static const struct snd_pcm_hardware hal2_pcm_hw = {
 	.info = (SNDRV_PCM_INFO_MMAP |
 		 SNDRV_PCM_INFO_MMAP_VALID |
 		 SNDRV_PCM_INFO_INTERLEAVED |
-		 SNDRV_PCM_INFO_BLOCK_TRANSFER),
+		 SNDRV_PCM_INFO_BLOCK_TRANSFER |
+		 SNDRV_PCM_INFO_SYNC_APPLPTR),
 	.formats =          SNDRV_PCM_FMTBIT_S16_BE,
 	.rates =            SNDRV_PCM_RATE_8000_48000,
 	.rate_min =         8000,
@@ -577,7 +578,6 @@ static int hal2_playback_trigger(struct snd_pcm_substream *substream, int cmd)
 	case SNDRV_PCM_TRIGGER_START:
 		hal2->dac.pcm_indirect.hw_io = hal2->dac.buffer_dma;
 		hal2->dac.pcm_indirect.hw_data = 0;
-		substream->ops->ack(substream);
 		hal2_start_dac(hal2);
 		break;
 	case SNDRV_PCM_TRIGGER_STOP: