ALSA: firewire-motu: fix stream format for MOTU 8pre FireWire

My previous refactoring for ALSA firewire-motu driver brought regression
to handle MOTU 8pre FireWire. The packet format is not operated correctly.

Cc: <stable@vger.kernel.org>
Fixes: dfbaa4dc ("ALSA: firewire-motu: add model-specific table of chunk count")
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20210614083133.39753-1-o-takashi@sakamocchi.jpSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/motu/motu-protocol-v2.c

@@ -353,6 +353,7 @@ const struct snd_motu_spec snd_motu_spec_8pre = {
 	.protocol_version = SND_MOTU_PROTOCOL_V2,
 	.flags = SND_MOTU_SPEC_RX_MIDI_2ND_Q |
 		 SND_MOTU_SPEC_TX_MIDI_2ND_Q,
-	.tx_fixed_pcm_chunks = {10, 6, 0},
-	.rx_fixed_pcm_chunks = {10, 6, 0},
+	// Two dummy chunks always in the end of data block.
+	.tx_fixed_pcm_chunks = {10, 10, 0},
+	.rx_fixed_pcm_chunks = {6, 6, 0},
 };