ramips/mt7620: Synchronize Makefiles with DTS compatible

ramips/mt7620: Synchronize Makefiles with DTS compatible

This will "rename" devices in Makefiles to the pattern used in
DTS compatible. This will systematize naming of devices
enormously.

As device names are used to for default SUPPORTED_DEVICES entries,
we need to adjust the source for /tmp/sysinfo/board_name, too.
So remove relevant entries from base-files/lib/ramips.sh and
use device compatible for that.

Despite that, base-files are updated, too.

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