Mark lantiq and omap as source only

[Alexander 'lynxis' Couzens]

Hi Paul,

> I haven’t seen much progress happening regarding bringing the targets lantiq or omap to Kernel 5.15. That fact is currently the last blocker for branching another release.

> Instead of postponing another release I’d like to mark both targets as source-only and do the 23.05 branch, starting with a RC0. If either of the two targets are fixed within the RC phase, they should be re-added, as discussed during the last meeting.

what are the problems with lantiq 5.15?

For omap:
- The upstream kernel changed the ethernet default and the driver will use 2 static vlan ids (configurable via dts) to tag the traffic
of port 1 and port 2.

ACK for OMAP. I'll try to fix it before the release.

Best,
lynxis