usb-core: Don't set packet state to complete on a nak

This way the hcd can re-use the same packet to retry without needing
to re-init it.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
diff --git a/hw/usb/core.c b/hw/usb/core.c
index 2da38e7..be6d936 100644
--- a/hw/usb/core.c
+++ b/hw/usb/core.c
@@ -399,8 +399,10 @@
              * otherwise packets can complete out of order!
              */
             assert(!p->ep->pipeline);
-            p->result = ret;
-            usb_packet_set_state(p, USB_PACKET_COMPLETE);
+            if (ret != USB_RET_NAK) {
+                p->result = ret;
+                usb_packet_set_state(p, USB_PACKET_COMPLETE);
+            }
         }
     } else {
         ret = USB_RET_ASYNC;