SUNRPC: Remove the tk_auth macro...

We should almost always be deferencing the rpc_auth struct by means of the
credential's cr_auth field instead of the rpc_clnt->cl_auth anyway. Fix up
that historical mistake, and remove the macro that propagated it.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 28a7894..50af8bb 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -787,7 +787,7 @@
 static void
 call_allocate(struct rpc_task *task)
 {
-	unsigned int slack = task->tk_auth->au_cslack;
+	unsigned int slack = task->tk_msg.rpc_cred->cr_auth->au_cslack;
 	struct rpc_rqst *req = task->tk_rqstp;
 	struct rpc_xprt *xprt = task->tk_xprt;
 	struct rpc_procinfo *proc = task->tk_msg.rpc_proc;