dt-bindings: display/msm: dp-controller: add X1E80100

Add X1E80100 to the dp-controller bindings, it has DisplayPort
controller similar to other platforms, but it uses its own compatible
string.

Signed-off-by: Abhinav Kumar <[e-mail]>
Signed-off-by: Jessica Zhang <[e-mail]>
Acked-by: Rob Herring (Arm) <[e-mail]>
Signed-off-by: Dmitry Baryshkov <[e-mail]>
Patchwork: https://patchwork.freedesktop.org/patch/672578/
Link: https://lore.kernel.org/r/[e-mail]

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

···
           - qcom,sdm845-dp
           - qcom,sm8350-dp
           - qcom,sm8650-dp
+          - qcom,x1e80100-dp
+
       - items:
           - enum:
               - qcom,sm6350-dp
···
             contains:
               enum:
                 - qcom,sa8775p-dp
+                - qcom,x1e80100-dp
       then:
         oneOf:
           - required: