SUNRPC: Allow the client to detect if the TCP connection is closed

Add an xprt->state bit to enable the TCP ->state_change() method to signal
whether or not the TCP connection is in the process of closing down.
This will to be used by the reconnection logic in a separate patch.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index 6f524a9..afb9e6a 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -257,6 +257,7 @@
 #define XPRT_CLOSE_WAIT		(3)
 #define XPRT_BOUND		(4)
 #define XPRT_BINDING		(5)
+#define XPRT_CLOSING		(6)
 
 static inline void xprt_set_connected(struct rpc_xprt *xprt)
 {