bcm63xx: remove model name from LED labels

bcm63xx: remove model name from LED labels

Like in the previous patches for various targets, this will remove
the "devicename" from LED labels in bcm63xx, as it's useless and
only creates complexity.

The devicename is removed in DTS files and 01_leds, merging
several cases on the way. A migration script is added for
existing configurations.

Note that a few labels were using "model::function" scheme without
color specified, those were converting to just "function" and the
necessary migrations were added to the migration script.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>