openflow_input: fix role_request/reply

Lists the role as enum ofp_controller role
Changes the body of the reply to match the body of the request as per spec
diff --git a/openflow_input/standard-1.2 b/openflow_input/standard-1.2
index 182794e..a22a259 100644
--- a/openflow_input/standard-1.2
+++ b/openflow_input/standard-1.2
@@ -1519,7 +1519,7 @@
     uint8_t type == 24;
     uint16_t length;
     uint32_t xid;
-    uint32_t role;
+    enum ofp_controller_role role;
     pad(4);
     uint64_t generation_id;
 };
@@ -1529,5 +1529,7 @@
     uint8_t type == 25;
     uint16_t length;
     uint32_t xid;
-    of_octets_t data;
+    enum ofp_controller_role role;
+    pad(4);
+    uint64_t generation_id;
 };