Without this fix N-type SOC devices like RTL8372N, RTL8383N and also the
4-port PHY RTL8224N, don't have a functional Serdes. Although the SOC
sees a link, there is no packet flow on both SFP-port nor RTL8224 ports.
Added helper functions to read/write to the RTL8224.
RTL8224 has the same register layout so we can use the same register
defines as for the main SOC.
logicog
René van Dorst