sfc: Run event/IRQ self-test asynchronously when interface is brought up

Generate a test event on each event queue whenever the interface is
brought up, then after 1 second check that we have either handled a
test event or handled another IRQ for each event queue.

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 e0e8596..f46e2ce 100644
--- a/drivers/net/ethernet/sfc/nic.h
+++ b/drivers/net/ethernet/sfc/nic.h
@@ -311,7 +311,7 @@
 
 static inline int efx_nic_event_test_irq_cpu(struct efx_channel *channel)
 {
-	return ACCESS_ONCE(channel->last_irq_cpu);
+	return ACCESS_ONCE(channel->event_test_cpu);
 }
 static inline int efx_nic_irq_test_irq_cpu(struct efx_nic *efx)
 {