dt-bindings: gpu: samsung-rotator: Document s5pv210 support

This commit documents new compatible for s5pv210 soc,
which will be also supported by this driver.

Signed-off-by: Paweł Chmiel <pawel.mikolaj.chmiel@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Inki Dae <inki.dae@samsung.com>