ALSA: firewire: Remove some left-over license text in sound/firewire

ALSA: firewire: Remove some left-over license text in sound/firewire

There is already a SPDX-License-Identifier tag, so the corresponding license
text can be removed.

While at it, be more consistent and:
  - add a missing .c (ff-protocol-latter)
  - remove an empty line (motu-protocol-v1)

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/2bfe76c7eeb0f5205a1427e280bf8d9da0354a62.1664110649.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Takashi Iwai <tiwai@suse.de>