ath79: enable gpio on ar933x by default

ath79: enable gpio on ar933x by default

All other SoC DTSI files have gpio enabled by default, only
ar9330/ar9331 disable it by default, only to have it enabled again
afterwards for each individual device.

So, do not disable it in the first place, and drop all device-specific
status statements afterwards.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>