dt-bindings: samsung: Document bindings for SGH-T959P board

Document the binding for Samsung Galaxy S Fascinate 4G (SGH-T959P).

Signed-off-by: Jonathan Bakker <xc-racer2@live.ca>
Signed-off-by: Paweł Chmiel <pawel.mikolaj.chmiel@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>