svcrdma: Add dma map count and WARN_ON

Add a dma map count in order to verify that all DMA mapping resources
have been freed when the transport is closed.

Signed-off-by: Tom Tucker <tom@opengridcomputing.com>
diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
index fd5e8a1..ab93afc 100644
--- a/include/linux/sunrpc/svc_rdma.h
+++ b/include/linux/sunrpc/svc_rdma.h
@@ -130,6 +130,7 @@
 
 	struct ib_pd         *sc_pd;
 
+	atomic_t	     sc_dma_used;
 	atomic_t	     sc_ctxt_used;
 	struct list_head     sc_ctxt_free;
 	int		     sc_ctxt_cnt;