SUNRPC: Allow caller to specify the transport to use

This is needed in order to allow the NFSv4.1 backchannel and
BIND_CONN_TO_SESSION function to work.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h
index 0b248e9..05a1809 100644
--- a/include/linux/sunrpc/sched.h
+++ b/include/linux/sunrpc/sched.h
@@ -103,6 +103,7 @@
 struct rpc_task_setup {
 	struct rpc_task *task;
 	struct rpc_clnt *rpc_client;
+	struct rpc_xprt *rpc_xprt;
 	const struct rpc_message *rpc_message;
 	const struct rpc_call_ops *callback_ops;
 	void *callback_data;