openpower: set layer compatibility to yocto 2.6

Change-Id: I728aaaf22fc92236f824868d40ccb494cddd295b
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/conf/layer.conf b/conf/layer.conf
index bb727b5..fafc941 100644
--- a/conf/layer.conf
+++ b/conf/layer.conf
@@ -8,7 +8,7 @@
 BBFILE_COLLECTIONS += "openpower-layer"
 BBFILE_PATTERN_openpower-layer = "^${LAYERDIR}/"
 LAYERVERSION_openpower-layer = "1"
-LAYERSERIES_COMPAT_openpower-layer = "sumo"
+LAYERSERIES_COMPAT_openpower-layer = "thud"
 
 # Provide a variable that points the base of the openpower layer.
 OPENPOWERBASE = '${@os.path.normpath("${LAYERDIR}/")}'