doc: release-notes-4.0: Add ethernet/mdio notes

[decsny]

Add release notes for ethernet and mdio drivers for 4.0

[pdgendt]

Check compliance issues

[jukkar]

I also added Ethernet stuff in #81216 but your changes look better so I removed the Ethernet driver part from mine.

[jukkar]

@decsny I am fine if you create the Ethernet driver release notes now and in the future. I just did it from old habit as there is no maintainer atm for Ethernet drivers. Perhaps you would like to volunteer to be a maintainer for the Ethernet drivers?

[decsny]

@jukkar sorry about this duplication, I didn't know someone else will do it. What is the difference between maintainer and collaborator ?

[jukkar]

sorry about this duplication, I didn't know someone else will do it.

No worries at all, I did not knew either that someone was writing the Ethernet driver part. Anyway, your PR looks good so we can use it for the notes.

What is the difference between maintainer and collaborator ?

See https://docs.zephyrproject.org/latest/project/project_roles.html