meta-facebook: upgrade to yocto 2.6

set layer compatability to thud

Change-Id: I4c5d03b2914b4ead10f0e4d79eb6d37f2d196bed
Signed-off-by: Vijay Khemka <vijaykhemka@fb.com>
diff --git a/conf/layer.conf b/conf/layer.conf
index 1aa60ce..59bdc48 100644
--- a/conf/layer.conf
+++ b/conf/layer.conf
@@ -7,4 +7,4 @@
 
 BBFILE_COLLECTIONS += "facebook-layer"
 BBFILE_PATTERN_facebook-layer = ""
-LAYERSERIES_COMPAT_facebook-layer = "sumo"
+LAYERSERIES_COMPAT_facebook-layer = "thud"