dt-bindings: display/msm: document the SM8550 DSI PHY

Document the SM8550 DSI PHY which is very close from the 7nm
and 5nm DSI PHYs found in earlier platforms.
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/517509/
Link: https://lore.kernel.org/r/20230103-topic-sm8550-upstream-mdss-dsi-v3-1-660c3bcb127f@linaro.orgSigned-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

Documentation/devicetree/bindings/display/msm/dsi-phy-7nm.yaml

@@ -20,6 +20,7 @@ properties:
       - qcom,sc7280-dsi-phy-7nm
       - qcom,sm8350-dsi-phy-5nm
       - qcom,sm8450-dsi-phy-5nm
+      - qcom,sm8550-dsi-phy-4nm
 
   reg:
     items: