switchdev: don't use anonymous union on switchdev attr/obj structs

Older gcc versions (e.g.  gcc version 4.4.6) don't like anonymous unions
which was causing build issues on the newly added switchdev attr/obj
structs.  Fix this by using named union on structs.

Signed-off-by: Scott Feldman <sfeldma@gmail.com>
Reported-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/bridge/br_stp.c b/net/bridge/br_stp.c
index b9300da..45f1ff1 100644
--- a/net/bridge/br_stp.c
+++ b/net/bridge/br_stp.c
@@ -41,7 +41,7 @@
 {
 	struct switchdev_attr attr = {
 		.id = SWITCHDEV_ATTR_PORT_STP_STATE,
-		.stp_state = state,
+		.u.stp_state = state,
 	};
 	int err;