ramips: add label MAC address for Mikrotik RB750Gr3
The device label contains:
E01: 74:4D:28:xx:xx:30
E05: 74:4D:28:xx:xx:34
The first value corresponds to the address set in hard_config 0x10.
That one is taken for the label MAC address.
Signed-off-by: Sven Roederer <[email protected]>