Most targets have been updated to consistently use the vendor_model
scheme for device definitions and thus, image names.
Apply this to bcm47xx as well. This does _not_ apply any other
specific naming changes.
Cc: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
d0cb71a896