MIPS: BCM63xx: Fix BCM6338 and BCM6345 gpio count

The number of GPIOs on BCM6338 is 8, while BCM6345 has only 16 GPIOs
available.

Signed-off-by: Florian Fainelli <florian@openwrt.org>
To: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/1016/


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