SUNRPC: fix variable type

Due to incorrect len type bc_send_request returned always zero.

The problem has been detected using proposed semantic patch
scripts/coccinelle/tests/assign_signed_to_unsigned.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2046107Signed-off-by: NAndrzej Hajda <a.hajda@samsung.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

net/sunrpc/xprtsock.c

@@ -2570,7 +2570,7 @@ static int bc_send_request(struct rpc_task *task)
 {
 	struct rpc_rqst *req = task->tk_rqstp;
 	struct svc_xprt	*xprt;
-	u32                     len;
+	int len;
 
 	dprintk("sending request with xid: %08x\n", ntohl(req->rq_xid));
 	/*