sfc: Do not assume efx_nic_type::ev_fini is idempotent

efx_fini_eventq() needs to be idempotent but EF10 firmware is
picky about queue states.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
diff --git a/drivers/net/ethernet/sfc/efx.c b/drivers/net/ethernet/sfc/efx.c
index 3977926..49d06ca 100644
--- a/drivers/net/ethernet/sfc/efx.c
+++ b/drivers/net/ethernet/sfc/efx.c
@@ -339,6 +339,7 @@
 	channel->eventq_read_ptr = 0;
 
 	efx_nic_init_eventq(channel);
+	channel->eventq_init = true;
 }
 
 /* Enable event queue processing and NAPI */
@@ -367,10 +368,14 @@
 
 static void efx_fini_eventq(struct efx_channel *channel)
 {
+	if (!channel->eventq_init)
+		return;
+
 	netif_dbg(channel->efx, drv, channel->efx->net_dev,
 		  "chan %d fini event queue\n", channel->channel);
 
 	efx_nic_fini_eventq(channel);
+	channel->eventq_init = false;
 }
 
 static void efx_remove_eventq(struct efx_channel *channel)