qemu/queue.h: simplify reverse access to QTAILQ

The new definition of QTAILQ does not require passing the headname,
remove it.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/net/net.c b/net/net.c
index 1f7d626..3acbdcc 100644
--- a/net/net.c
+++ b/net/net.c
@@ -563,7 +563,7 @@
             }
         }
     } else {
-        QTAILQ_FOREACH_REVERSE(nf, &nc->filters, NetFilterHead, next) {
+        QTAILQ_FOREACH_REVERSE(nf, &nc->filters, next) {
             ret = qemu_netfilter_receive(nf, direction, sender, flags, iov,
                                          iovcnt, sent_cb);
             if (ret) {