release notes: mention mctp changes

[igaw]

As far as I am aware, there is minimal external usage of the dbus-based device enumeration at present, so a changeover should have minimal impact. Might be worth a mention in the libnvme changelog though.

Originally posted by @jk-ozlabs in #929 (comment)

[jk-ozlabs]

If you need some text for that:

This release switches to the newer dbus API for mctpd (corresponding to mctpd version 2.0 and later). If you're using libnvme's MCTP-device endpoint enumeration functions (nvme_mi_for_each_endpoint), you will need to update to mctpd v2.x or later.

of course, feel free to adjust for suitability for the notes format.