ALSA: bebob: code refactoring for M-Audio models

For M-Audio FireWire 410, the value of immediate entry for vendor in unit
directory is the value for BridgeCo. AG OUI. It seems that M-Audio uses
initial settings as is for its product.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20210611093730.78254-6-o-takashi@sakamocchi.jp


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