lantiq: show xdsl line init status on shared dsl/internet led

lantiq: show xdsl line init status on shared dsl/internet led

On boards which don't have a distinct internet and dsl led, use the
shared LED to indicate the xdsl line state and any traffic that is
send/received via the netdev. This traffic doesn't necessarily need to
be internet traffic.

Rename the shared LED of existing configs to "dsl", to match the new
defaults. The configuration of the to be renamed LED is identical with
the new defaults.

Signed-off-by: Mathias Kresin <dev@kresin.me>