layer.conf: add kirkstone to LAYERSERIES_COMPAT

Signed-off-by: Christian Eggers <ceggers@arri.de>

conf/layer.conf

@@ -9,6 +9,6 @@ BBFILE_COLLECTIONS += "swupdate"
 BBFILE_PATTERN_swupdate := "^${LAYERDIR}/"
 BBFILE_PRIORITY_swupdate = "6"
 
-LAYERSERIES_COMPAT_swupdate = "dunfell hardknott honister"
+LAYERSERIES_COMPAT_swupdate = "dunfell hardknott honister kirkstone"
 
 LAYERDEPENDS_swupdate = "openembedded-layer"