lantiq: make AVM FRITZ!Box naming consistent

lantiq: make AVM FRITZ!Box naming consistent

This commit changes the model string and device title of all AVM boards
to fit the naming of the manufacturer.

Drop all provider-specific titles as they are re-used for every device
generation by 1&1. The original AVM model name is printed on the bottom
of every devices.

Exception applies for boards which are only supported by a specific
sub-revision.

Signed-off-by: David Bauer <mail@david-bauer.net>