sfc: Really disable flow control while flushing

Receiving pause frames can block TX queue flushes.  Earlier changes
work around this by reconfiguring the MAC during flushes for VFs, but
during flushes for the PF we would only change the fc_disable counter.
Unless the MAC is reconfigured for some other reason during the flush
(which I would not expect to happen) this had no effect at all.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
diff --git a/drivers/net/ethernet/sfc/nic.h b/drivers/net/ethernet/sfc/nic.h
index 7a9647a..1b000332 100644
--- a/drivers/net/ethernet/sfc/nic.h
+++ b/drivers/net/ethernet/sfc/nic.h
@@ -344,6 +344,8 @@
 
 /* Global Resources */
 extern int efx_nic_flush_queues(struct efx_nic *efx);
+extern void siena_prepare_flush(struct efx_nic *efx);
+extern void siena_finish_flush(struct efx_nic *efx);
 extern void falcon_start_nic_stats(struct efx_nic *efx);
 extern void falcon_stop_nic_stats(struct efx_nic *efx);
 extern void falcon_setup_xaui(struct efx_nic *efx);