ipq806x: ap148/r7500: fix eth0 for non gige speeds

ipq806x: ap148/r7500: fix eth0 for non gige speeds

Eth0 is attached to mac0 of the switch with a fixed link and and not to
phy4 in single phy mode, so configuring it to anything but 1000FD will
break the connection, which will happen if a only 100 Mbit capapble device
is plugged into the wan port.

Fix this by not taking the state from phy4 and just configuring a fixed link
for eth0.

Signed-off-by: Jonas Gorski <jogo@openwrt.org>
SVN-Revision: 47695