fonbase: Remove private wifi mtu hack for 2.0g.
This hack raised the mtu of the private wifi signal to 1504 (instead of
the default 1500). This was needed because packets coming in from the
LAN interface that were bridged to the private wifi interface were 4
bytes to long.
This issue was properly fixed in the mvswitch driver in r1810, so this
workaround is no longer needed.
