[patches] add fix for mac address issues for wdr4900

see #122
[packages] ffwizard-berlin set mac addr if present

On some devices (like WDR4900) mac address is set in /etc/config/network.
For dhcp interface we reuse this mac from lan (which afterwards gets deleted).
Merge pull request #128 from freifunk-berlin/features/wdr4900_mac_fix

[patches] add fix for mac address issue for wdr4900