dt-bindings: display/msm: Document the DPU for QCS8300

dt-bindings: display/msm: Document the DPU for QCS8300

Document the DPU for Qualcomm QCS8300 platform. It use the same DPU
hardware with SA8775P and reuse it's driver.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Yongxing Mou <yongxing.mou@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/684198/
Link: https://lore.kernel.org/r/20251029-qcs8300_mdss-v13-1-e8c8c4f82da2@oss.qualcomm.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>