SUNRPC: Make rpc_clnt store the multipath iterators

This is a pre-patch for the RPC multipath code. It sets up the storage in
struct rpc_clnt for the multipath code.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
index 0c5c2cb..1713e41 100644
--- a/include/linux/sunrpc/clnt.h
+++ b/include/linux/sunrpc/clnt.h
@@ -25,6 +25,7 @@
 #include <asm/signal.h>
 #include <linux/path.h>
 #include <net/ipv6.h>
+#include <linux/sunrpc/xprtmultipath.h>
 
 struct rpc_inode;
 
@@ -67,6 +68,7 @@
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 	struct dentry		*cl_debugfs;	/* debugfs directory */
 #endif
+	struct rpc_xprt_iter	cl_xpi;
 };
 
 /*