nuvoton: Set LAYERSERIES_COMPAT

Bitbake warns when this variable is not set for a layer. Set it in the
Nuvoton BSP and EVB layers to indicate sumo branch compatiblity.

Change-Id: If2dd63954ca88d0dc4e0427eb6c3ccf035681585
Signed-off-by: Benjamin Fair <benjaminfair@google.com>
diff --git a/conf/layer.conf b/conf/layer.conf
index 1fefedb..fe22772 100644
--- a/conf/layer.conf
+++ b/conf/layer.conf
@@ -7,3 +7,4 @@
 BBFILE_COLLECTIONS += "nuvoton-layer"
 BBFILE_PATTERN_nuvoton-layer = ""
 LAYERVERSION_nuvoton-layer = "1"
+LAYERSERIES_COMPAT_nuvoton-layer = "sumo"