meta-evb-aspeed: Declare layer compatibility

Avoids this warning:

 WARNING: Layer evb-ast2500 should set LAYERSERIES_COMPAT_evb-ast2500 in
 its conf/layer.conf file to list the core layer names it is compatible
 with.

Change-Id: If580b22ff01eec259cd7fd1f0ead90a4b2327418
Signed-off-by: Joel Stanley <joel@jms.id.au>
diff --git a/meta-evb/meta-evb-aspeed/conf/layer.conf b/meta-evb/meta-evb-aspeed/conf/layer.conf
index 6d78f95..369f84d 100644
--- a/meta-evb/meta-evb-aspeed/conf/layer.conf
+++ b/meta-evb/meta-evb-aspeed/conf/layer.conf
@@ -3,3 +3,5 @@
 
 BBFILE_COLLECTIONS += "evb-aspeed"
 BBFILE_PATTERN_evb-aspeed = ""
+
+LAYERSERIES_COMPAT_evb-aspeed-layer = "honister kirkstone"