ALSA: firewire-lib: delete unused kernel API

No driver use snd_fw_schedule_registration(). Let's delete it.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20210607081250.13397-10-o-takashi@sakamocchi.jp


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