dt-bindings: net: qcom,ethqos: Add Qualcomm sc8280xp compatibles

The sc8280xp has a new version of the ETHQOS hardware in it, EMAC v3.
Add a compatible for this.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
Tested-by: Brian Masney <bmasney@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>