MIPS: AR7: Fix double ar7_gpio_init declaration

Signed-off-by: Florian Fainelli <florian@openwrt.org>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/1748/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>