ar71xx: fix swapped LAN/WAN MAC address for Archer C60 v1/v2

ar71xx: fix swapped LAN/WAN MAC address for Archer C60 v1/v2

The MAC addresses for lan/wan are swapped compared to the vendor
firmware. This adjusts to vendor configuration, which is:

lan   *:7b   label
wan   *:7c   label+1
2.4g  *:7b   label
5g    *:7a   label-1

Only one address is stored in <&mac 0x8>, corresponding to the label.

This has been checked on revisions v1, v2 and v3.

Since ar71xx calculates the ath10k MAC address based on the ethernet
addresses, the number there is adjusted, too.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
(cherry picked from commit 14eb54938b525d4c2d2847a6fad7670ed944650c)