meta-openpower: layer.conf: change BBFILE_PATTERN

Use the immmediate expansion operator when setting BBFILE_PATTERN.  This
makes meta-openpower consistent with all the layers in
meta-openembedded.

(From meta-openpower rev: f03263407a5f328c6df479c3a1148e663a9e8078)

Change-Id: I10c02ab946efd111c12f9fd80526a7cbeae3129c
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/meta-openpower/conf/layer.conf b/meta-openpower/conf/layer.conf
index fc6453c..6bc20a4 100644
--- a/meta-openpower/conf/layer.conf
+++ b/meta-openpower/conf/layer.conf
@@ -6,7 +6,7 @@
             ${LAYERDIR}/recipes-*/*/*.bbappend"
 
 BBFILE_COLLECTIONS += "openpower-layer"
-BBFILE_PATTERN_openpower-layer = "^${LAYERDIR}/"
+BBFILE_PATTERN_openpower-layer := "^${LAYERDIR}/"
 LAYERVERSION_openpower-layer = "1"
 LAYERSERIES_COMPAT_openpower-layer = "thud warrior"