virtio-net: remove function calls from assert

peer_{de,at}tach were called from inside assert().
We don't support building without NDEBUG but it's not tidy.
Rearrange to attach peer outside assert calls.

Signed-off-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/net/virtio-net.c

@@ -397,12 +397,15 @@ static int peer_detach(VirtIONet *n, int index)
 static void virtio_net_set_queues(VirtIONet *n)
 {
     int i;
+    int r;
 
     for (i = 0; i < n->max_queues; i++) {
         if (i < n->curr_queues) {
-            assert(!peer_attach(n, i));
+            r = peer_attach(n, i);
+            assert(!r);
         } else {
-            assert(!peer_detach(n, i));
+            r = peer_detach(n, i);
+            assert(!r);
         }
     }
 }