MIPS: ath79: Fix number of GPIO lines for AR724[12]

The AR724[12] SoCs have more GPIO lines than the AR7240.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Cc: Cc: linux-mips@linux-mips.org
Patchwork: https://http://patchwork.linux-mips.org/patch/4167/


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