dt-bindings: samsung,mipi-dsim: Use port-base reference

Use port-base reference for port@1.

This fixes the following schema warning:

imx8mp-dhcom-pdk3.dtb: dsi@32e60000: ports:port@1:endpoint: Unevaluated properties are not allowed ('data-lanes' was unexpected)
From schema: Documentation/devicetree/bindings/display/bridge/samsung,mipi-dsim.yaml

Fixes: 1f0d40d88f7a ("dt-bindings: bridge: Convert Samsung MIPI DSIM bridge to yaml")
Signed-off-by: Fabio Estevam <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
[narmstrong: removed line break between tags]
Signed-off-by: Neil Armstrong <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

Documentation/devicetree/bindings/display/bridge/samsung,mipi-dsim.yaml

···
           specified.
 
       port@1:
-        $ref: /schemas/graph.yaml#/properties/port
+        $ref: /schemas/graph.yaml#/$defs/port-base
+        unevaluatedProperties: false
         description:
           DSI output port node to the panel or the next bridge
           in the chain.