treewide: remove gategarth from layer-support

We've typically kept these LAYERSERIES_COMPAT to 2 releases: the current
and the upcoming.  Remove 'gatesgarth' is it is now 2 releases back.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I5e812a94fed1738898af75c0fdee81996a5bbf20
diff --git a/meta-lenovo/conf/layer.conf b/meta-lenovo/conf/layer.conf
index 180e960..0b7cb4f 100644
--- a/meta-lenovo/conf/layer.conf
+++ b/meta-lenovo/conf/layer.conf
@@ -12,7 +12,7 @@
 BBFILE_COLLECTIONS += "lenovo-layer"
 BBFILE_PATTERN_lenovo-layer = ""
 LAYERVERSION_lenovo-layer = "1"
-LAYERSERIES_COMPAT_lenovo-layer = "gatesgarth hardknott"
+LAYERSERIES_COMPAT_lenovo-layer = "hardknott"
 
 # Provide a variable that points the base of the lenovo layer.
 LENOVOBASE = '${@os.path.normpath("${LAYERDIR}/")}'
diff --git a/meta-lenovo/meta-hr630/conf/layer.conf b/meta-lenovo/meta-hr630/conf/layer.conf
index 9c1b4d6..2c6117c 100644
--- a/meta-lenovo/meta-hr630/conf/layer.conf
+++ b/meta-lenovo/meta-hr630/conf/layer.conf
@@ -11,4 +11,4 @@
 BBFILE_COLLECTIONS += "hr630-layer"
 BBFILE_PATTERN_hr630-layer = ""
 BBFILE_PRIORITY_hr630-layer = "5"
-LAYERSERIES_COMPAT_hr630-layer = "gatesgarth hardknott"
+LAYERSERIES_COMPAT_hr630-layer = "hardknott"
diff --git a/meta-lenovo/meta-hr855xg2/conf/layer.conf b/meta-lenovo/meta-hr855xg2/conf/layer.conf
index 3641432..2af2de1 100644
--- a/meta-lenovo/meta-hr855xg2/conf/layer.conf
+++ b/meta-lenovo/meta-hr855xg2/conf/layer.conf
@@ -11,4 +11,4 @@
 BBFILE_COLLECTIONS += "hr855xg2-layer"
 BBFILE_PATTERN_hr855xg2-layer := "^${LAYERDIR}/"
 BBFILE_PRIORITY_hr855xg2-layer = "5"
-LAYERSERIES_COMPAT_hr855xg2-layer = "gatesgarth hardknott"
+LAYERSERIES_COMPAT_hr855xg2-layer = "hardknott"