dt-bindings: gpio: msc313: Add offsets for ssd20xd

Add the gpio offsets for the SSD201 and SSD202D chips.

Signed-off-by: Daniel Palmer <daniel@0x0f.com>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>