kernel-resin.bbclass: Add support for aufs 4.14.56+
kernel-resin.bbclass: Add support for aufs 4.14.56+

Change-type: minor
Changelog-entry: Add support for aufs 4.14.56+
Signed-off-by: Florin Sarbu <3a837a37a2ac9072a088641ec330e0e5d5b86f4e@resin.io>

resin-os/meta-resin,resin-os/meta-resin,resin-os/meta-resin,resin-os/meta-resin