dt-bindings: msm: dsi-controller-main: document the SA8775P DSI CTRL

Document the DSI CTRL on the SA8775P Platform.

Signed-off-by: Ayushi Makhija <quic_amakhija@quicinc.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/649855/
Link: https://lore.kernel.org/r/20250424062431.2040692-3-quic_amakhija@quicinc.com


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>