In 2011 (!), network setup for nexaira,bc2 was moved to network
defaults script with a typo so it became b2c:
295e04084c ("ramips: setup bc2 mac addresses from the generic network script")
This patch just removes the useless entry without replacement,
since it seems to have worked for 8 years anyway.
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>