meta-facebook: upgrade to yocto 2.6

set layer compatability to thud

(From meta-facebook rev: f3275f5f3161f23fe2610417265d12577e69540a)

Change-Id: I6ab2683f7c2996ad31a6c8e0579428fdb5b892e7
Signed-off-by: Vijay Khemka <vijaykhemka@fb.com>
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/meta-facebook/conf/layer.conf b/meta-facebook/conf/layer.conf
index 1aa60ce..59bdc48 100644
--- a/meta-facebook/conf/layer.conf
+++ b/meta-facebook/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"