xprtrdma: Fix an frwr_map recovery nit

After a DMA map failure in frwr_map, mark the MR so that recycling
won't attempt to DMA unmap it.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Fixes: e2f34e2671 ("xprtrdma: Yet another double DMA-unmap")
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/xprtrdma/frwr_ops.c

@@ -466,7 +466,7 @@ struct rpcrdma_mr_seg *frwr_map(struct rpcrdma_xprt *r_xprt,
 	return seg;
 
 out_dmamap_err:
-	frwr->fr_state = FRWR_IS_INVALID;
+	mr->mr_dir = DMA_NONE;
 	trace_xprtrdma_frwr_sgerr(mr, i);
 	rpcrdma_mr_put(mr);
 	return ERR_PTR(-EIO);