xprtrdma: Clean up XDR decoding in rpcrdma_update_granted_credits()

Clean up: Replace C-structure based XDR decoding for consistency
with other areas.

struct rpcrdma_rep is rearranged slightly so that the relevant fields
are in cache when the Receive completion handler is invoked.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index d4a897a..52e73ea 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -220,13 +220,13 @@ struct rpcrdma_rep {
 	struct ib_cqe		rr_cqe;
 	int			rr_wc_flags;
 	u32			rr_inv_rkey;
+	struct rpcrdma_regbuf	*rr_rdmabuf;
 	struct rpcrdma_xprt	*rr_rxprt;
 	struct work_struct	rr_work;
 	struct xdr_buf		rr_hdrbuf;
 	struct xdr_stream	rr_stream;
 	struct list_head	rr_list;
 	struct ib_recv_wr	rr_recv_wr;
-	struct rpcrdma_regbuf	*rr_rdmabuf;
 };
 
 /*