dt-bindings: net: snps,dwmac: Add Qualcomm Ethernet ETHQOS compatibles

Add Qualcomm Ethernet ETHQOS compatible checks
in snps,dwmac YAML binding document.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bhupesh Sharma <bhupesh.sharma@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>