MIPS: BCM63xx: Fix GPIO set/get for BCM6345

On BCM6345, the register offsets for the set/get GPIO registers is wrong.
Use the same logic as the one present in arch/mips/bcm63xx/irq.c to
define the correct gpio_out_low_reg value when support for BCM6345
is compiled in.

Signed-off-by: Florian Fainelli <florian@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3010/


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