ALSA: firewire-motu: remove obsoleted codes

The way to decide CIP payload size by calculation with any flag is now
obsoleted. This commit removes the codes.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20200519111641.123211-12-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Iwai <tiwai@suse.de>