netdevsim: fix duplicated debugfs directory

The "ethtool" debugfs directory holds per-netdev knobs, so move
it from the device instance directory to the port directory.

This fixes the following warning when creating multiple ports:

 debugfs: Directory 'ethtool' with parent 'netdevsim1' already present!

Fixes: ff1f7c1 ("netdevsim: add pause frame stats")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/netdevsim/ethtool.c

@@ -54,7 +54,7 @@ void nsim_ethtool_init(struct netdevsim *ns)
 
 	ns->netdev->ethtool_ops = &nsim_ethtool_ops;
 
-	ethtool = debugfs_create_dir("ethtool", ns->nsim_dev->ddir);
+	ethtool = debugfs_create_dir("ethtool", ns->nsim_dev_port->ddir);
 
 	dir = debugfs_create_dir("pause", ethtool);
 	debugfs_create_bool("report_stats_rx", 0600, dir,

tools/testing/selftests/drivers/net/netdevsim/ethtool-pause.sh

@@ -3,7 +3,7 @@
 
 NSIM_ID=$((RANDOM % 1024))
 NSIM_DEV_SYS=/sys/bus/netdevsim/devices/netdevsim$NSIM_ID
-NSIM_DEV_DFS=/sys/kernel/debug/netdevsim/netdevsim$NSIM_ID
+NSIM_DEV_DFS=/sys/kernel/debug/netdevsim/netdevsim$NSIM_ID/ports/0
 NSIM_NETDEV=
 num_passes=0
 num_errors=0