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.jp


Signed-off-by: Takashi Iwai <tiwai@suse.de>