ath79: use internal switch for EAP300 v2

ath79: use internal switch for EAP300 v2

Have the port use GMAC1 with internal switch
which fixes the issue of the ethernet LED not functioning
The LED is triggered by the internal switch, not a GPIO.

The GPIO for the ethernet LED was added in ath79
as it was defined in the ar71xx target
but it was not functioning in ath79 for a previously unknown reason.

It is unknown why that GPIO was defined as an LED in ar71xx.

Signed-off-by: Michael Pratt <mcpratt@pm.me>
[drop unrelated changes: model property and SPI max frequency]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>