spapr_llan: fix device reenabling

Normally, the "tap" device is polled by QEMU if a guest NIC can
receive packets. If a guest NIC is stopped during transfer (rmmod or
ifdown), it may still have packets in a queue which have to be send
to the guest before QEMU enables polling of a "tap" interface via
tap_update_fd_handler().

However the spapr_llan device was missing the qemu_flush_queued_packets()
call so the tap_send_completed() callback was never called and therefore
"tap" interface polling was not enabled ever.

The patch fixes this problem.
Signed-off-by: NAlexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: NAlexander Graf <agraf@suse.de>

hw/net/spapr_llan.c

@@ -336,6 +336,8 @@ static target_ulong h_register_logical_lan(PowerPCCPU *cpu,
     spapr_vio_dma_set(sdev, VLAN_BD_ADDR(rec_queue), 0, VLAN_BD_LEN(rec_queue));
 
     dev->isopen = 1;
+    qemu_flush_queued_packets(qemu_get_queue(dev->nic));
+
     return H_SUCCESS;
 }