meta-lenovo: update Yocto compat for gatesgarth

The next release of Yocto is soon and most of the upstream
layers have switched support strings for it.  Support layer
compat for gatesgarth (current) and dunsfell (previous).

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ic1a1d5ed9706e272f8ce0e2d4f17ef8328799390
diff --git a/conf/layer.conf b/conf/layer.conf
index 30d2bbc..b18d1ea 100644
--- a/conf/layer.conf
+++ b/conf/layer.conf
@@ -12,7 +12,7 @@
 BBFILE_COLLECTIONS += "lenovo-layer"
 BBFILE_PATTERN_lenovo-layer = ""
 LAYERVERSION_lenovo-layer = "1"
-LAYERSERIES_COMPAT_lenovo-layer = "thud warrior"
+LAYERSERIES_COMPAT_lenovo-layer = "dunfell gatesgarth"
 
 # Provide a variable that points the base of the lenovo layer.
 LENOVOBASE = '${@os.path.normpath("${LAYERDIR}/")}'