ar71xx: improve support for the My Net Wi-Fi Range Extender device

ar71xx: improve support for the My Net Wi-Fi Range Extender device

This patch improves support for the device considerably.

1. The wifi didn't work in the initial release. This was because
the WMAC of the AR9340 is not connected to the antennas.
(However, it can pick up wifi signals, if they are strong enough!)
Instead there's a dedicated AR9300 chip on the same board, which
works.

2. Ethernet throughput is improved. iperf shows that the hardware
can sustain more than 200Mbit/s and no longer drops any packages
when the link is under load.

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Patchwork: http://patchwork.openwrt.org/patch/4461/
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38949 3c298f89-4303-0410-b956-a3cf2f4a3e73