ramips: add label MAC address for Mikrotik RBM33G

The device label contains:
E01: B8:69:F4:xx:xx:07
E02: B8:69:F4:xx:xx:09

The first value corresponds to the address set in hard_config 0x10.

That one is taken for the label MAC address.

Thanks to Martin Schiller for retrieving the information.

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