nouveau: off by one in nv50_gpio_location()

If "gpio->line" is 32 then "nv50_gpio_reg[gpio->line >> 3]" reads past the
end of the array.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>