net: stmmac: dwmac-qcom-ethqos: Add EMAC3 support

Add the new programming sequence needed for EMAC3 based platforms such
as the sc8280xp family.

Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Brian Masney <bmasney@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>