ARM: pxa: DTS: override gpio node in pxa3xx.dtsi

The gpio controller node inherited from pxa2xx.dtsi won't work for
pxa3xx SoCs, so let's override it in pxa3xx.dtsi.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Cc: Haojian Zhuang <haojian.zhuang@linaro.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>