meta-agl-kvm-demo: fix layer compatibility

I missed checking in the LAYERSERIES_COMPAT bump for scarthgap after
cherry-picking the meta-agl-kvm-demo changes to master, update it
so the layer is usable.

Bug-AGL: SPEC-5138

Change-Id: I450cba7a5f68636f9d13cd429c8159fd6cc2ace9
Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl-demo/+/29956
ci-image-build: Jenkins Job builder account
Tested-by: Jenkins Job builder account
ci-image-boot-test: Jenkins Job builder account