meta-openpower: layer.conf: Add warrior compatibility

oe-core branched in preparation for the upcoming 2.7 Yocto release and
as of 13e45ff requires core layer compatibility to "warrior" instead of
"thud".  We'll retain compatibility for both until we do our own branch
or stop testing thud.

Change-Id: I840dfc379f37d4bd660d7ca0ba93501e8286bbf4
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/conf/layer.conf b/conf/layer.conf
index fafc941..fc6453c 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 = "thud"
+LAYERSERIES_COMPAT_openpower-layer = "thud warrior"
 
 # Provide a variable that points the base of the openpower layer.
 OPENPOWERBASE = '${@os.path.normpath("${LAYERDIR}/")}'