ALSA: dice: Add support for MIDI capture/playback

This commit adds a support for MIDI capture/playback

When MIDI substrams already start streaming and PCM substreams are going to
join at different sampling rate, streams are stopped once. Then sampling rate
is changed and streams are restarted.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Acked-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/dice/dice-stream.c

@@ -218,6 +218,8 @@ int snd_dice_stream_start_duplex(struct snd_dice *dice, unsigned int rate)
 			"fail to get sampling rate\n");
 		goto end;
 	}
+	if (rate == 0)
+		rate = curr_rate;
 	if (rate != curr_rate)
 		stop_stream(dice, master);