dt-bindings: display/msm: dp-controller: document QCS8300 compatible

Add compatible string for the DisplayPort controller found on the
Qualcomm QCS8300 SoC.

The Qualcomm QCS8300 platform comes with one DisplayPort controller
that supports 4 MST streams, similar to the one found on the SA8775P.

Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Yongxing Mou <[e-mail]>
Patchwork: https://patchwork.freedesktop.org/patch/684200/
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Baryshkov <[e-mail]>

Documentation/devicetree/bindings/display/msm/dp-controller.yaml

···
 
       - items:
           - enum:
+              - qcom,qcs8300-dp
+          - const: qcom,sa8775p-dp
+
+      - items:
+          - enum:
               - qcom,sm6350-dp
           - const: qcom,sc7180-dp