ipq40xx: add label MAC address for Netgear EX6100v2/EX6150v2

ipq40xx: add label MAC address for Netgear EX6100v2/EX6150v2

This is based on the EX6150v2, which should be identical to
the EX6100v2:

The device bears two MAC addresses ("MAC 1" and "MAC 2") that
correspond to phy0 and phy1.

The ethernet MAC address (gmac0) is the same as phy0.
As this one is accessible via local-mac-address in gmac0, the
latter is used for label-mac-device.

(Although this is a one-port, gmac1 also has a local-mac-address
assigned. This has the same vendor part as the other addresses,
but completely different data for the device part.)

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