ALSA: firewire-motu: remove TODO for interaction with userspace about control message

Now UAPI of ALSA firewire stack got enough functions to interact with
userspace for protocol of MOTU FireWire series. Let's remove the relevant
TODO.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20211029012847.11839-1-o-takashi@sakamocchi.jp


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