xprtrdma: Fix error code in rpcrdma_buffer_create()

This should return -ENOMEM if __alloc_workqueue_key() fails, but it
returns success.

Fixes: 6d2d0ee2 ("xprtrdma: Replace rpcrdma_receive_wq with a per-xprt workqueue")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/xprtrdma/verbs.c

@@ -1113,8 +1113,10 @@ rpcrdma_buffer_create(struct rpcrdma_xprt *r_xprt)
 						WQ_MEM_RECLAIM | WQ_HIGHPRI,
 						0,
 			r_xprt->rx_xprt.address_strings[RPC_DISPLAY_ADDR]);
-	if (!buf->rb_completion_wq)
+	if (!buf->rb_completion_wq) {
+		rc = -ENOMEM;
 		goto out;
+	}
 
 	return 0;
 out: