dt-bindings: display: rocktech,jh057n00900: Document panel rotation

Document the rotation property for rocktech,jh057n00900 panels.

Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Guido Günther <agx@sigxcpu.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20240212184950.52210-4-macroalpha82@gmail.com