ALSA: fireface: make read-only const array for model names static

It is preferable not to populate the constant array for constant strings
on the stack.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20230627235406.289970-1-o-takashi@sakamocchi.jp


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