AA: ar71xx: don't use the unknown LED on the ZCN-1523-5 board

AA: ar71xx: don't use the unknown LED on the ZCN-1523-5 board

Backport of r34076.

According to #12421, GPIO 1 controls the power
output on the unused lines of the LAN2 port.
Remove the LED definition in order to prevent
possible permanent hardware damage.

If someone needs that, the power-out feature can
be controlled via the GPIO sysfs interface.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
git-svn-id: svn://svn.openwrt.org/openwrt/branches/attitude_adjustment@34077 3c298f89-4303-0410-b956-a3cf2f4a3e73