net/queue: queue packets even if sender doesn't supply a callback

Now that we disable any receiver whose queue is full, we do not require
senders to handle a zero return by supplying a sent callback.

This is a second step towards allowing can_receive() handlers to return
true even if no buffer space is available.

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

net/queue.c

@@ -186,7 +186,7 @@ ssize_t qemu_net_queue_send(NetQueue *queue,
     }
 
     ret = qemu_net_queue_deliver(queue, sender, flags, data, size);
-    if (ret == 0 && sent_cb != NULL) {
+    if (ret == 0) {
         qemu_net_queue_append(queue, sender, flags, data, size, sent_cb);
         return 0;
     }
@@ -210,7 +210,7 @@ ssize_t qemu_net_queue_send_iov(NetQueue *queue,
     }
 
     ret = qemu_net_queue_deliver_iov(queue, sender, flags, iov, iovcnt);
-    if (ret == 0 && sent_cb != NULL) {
+    if (ret == 0) {
         qemu_net_queue_append_iov(queue, sender, flags, iov, iovcnt, sent_cb);
         return 0;
     }
@@ -246,7 +246,7 @@ void qemu_net_queue_flush(NetQueue *queue)
                                      packet->flags,
                                      packet->data,
                                      packet->size);
-        if (ret == 0 && packet->sent_cb != NULL) {
+        if (ret == 0) {
             QTAILQ_INSERT_HEAD(&queue->packets, packet, entry);
             break;
         }