xprtrdma: Move struct ib_send_wr off the stack

For FRWR FASTREG and LOCAL_INV, move the ib_*_wr structure off
the stack. This allows frwr_op_map and frwr_op_unmap to chain
WRs together without limit to register or invalidate a set of MRs
with a single ib_post_send().

(This will be for chaining LOCAL_INV requests).

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: Devesh Sharma <devesh.sharma@avagotech.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 ac7f8d4..5c1e0c6 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -207,6 +207,10 @@
 	enum rpcrdma_frmr_state		fr_state;
 	struct work_struct		fr_work;
 	struct rpcrdma_xprt		*fr_xprt;
+	union {
+		struct ib_reg_wr	fr_regwr;
+		struct ib_send_wr	fr_invwr;
+	};
 };
 
 struct rpcrdma_fmr {