[OE-core] Update layer compatibility to Dunfell

[nick83ola]

Hi,
is it time to update the layer compatibility for meta* to dunfell?

Especially because after change

    commit 9702544b3e75d761d86cae7e8b36f3f2625b68ce
    Author: Denys Dmytriyenko <denys at ti.com>
    Date:   Thu Nov 14 19:40:07 2019 -0500

    distro_features_check: expand with MACHINE_FEATURES and COMBINED_FEATURES,
    rename

a lot of recipes start throwing warnings.

The change

    commit 98e34b71ef54fdada2fdc199905f8f2dfae7e933
    Author: Scott Rifenbark <srifenbark at gmail.com>
    Date:   Wed Dec 11 13:02:24 2019 -0800
    poky.ent: Updated variables for YP 3.1

already changed the release name

Thanks
Nicola Lunghi