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: 1f0d40d8 ("dt-bindings: bridge: Convert Samsung MIPI DSIM bridge to yaml")
Signed-off-by: Fabio Estevam <festevam@denx.de>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
[narmstrong: removed line break between tags]
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230531224407.1611952-1-festevam@gmail.com