xprtrdma: Add "destroy MRs" memreg op

Memory Region objects associated with a transport instance are
destroyed before the instance is shutdown and destroyed.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Tested-by: Devesh Sharma <Devesh.Sharma@Emulex.Com>
Tested-by: Meghana Cheripady <Meghana.Cheripady@Emulex.Com>
Tested-by: Veeresh U. Kokatnur <veereshuk@chelsio.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 0680239..b95e223 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -343,6 +343,7 @@
 	size_t		(*ro_maxpages)(struct rpcrdma_xprt *);
 	int		(*ro_init)(struct rpcrdma_xprt *);
 	void		(*ro_reset)(struct rpcrdma_xprt *);
+	void		(*ro_destroy)(struct rpcrdma_buffer *);
 	const char	*ro_displayname;
 };