netlink: do not allocate a device refcount tracker in ethnl_default_notify()

As reported by Johannes, the tracker allocated in
ethnl_default_notify() is not really needed, as this
function is not expected to change a device reference count.

Fixes: e4b89540 ("netlink: add net device refcount tracker to struct ethnl_req_info")
Signed-off-by: NEric Dumazet <edumazet@google.com>
Reported-by: NJohannes Berg <johannes@sipsolutions.net>
Tested-by: NJohannes Berg <johannes@sipsolutions.net>
Link: https://lore.kernel.org/r/20220105170849.2610470-1-eric.dumazet@gmail.comSigned-off-by: NJakub Kicinski <kuba@kernel.org>

net/ethtool/netlink.c

@@ -627,7 +627,6 @@ static void ethnl_default_notify(struct net_device *dev, unsigned int cmd,
 	}
 
 	req_info->dev = dev;
-	netdev_tracker_alloc(dev, &req_info->dev_tracker, GFP_KERNEL);
 	req_info->flags |= ETHTOOL_FLAG_COMPACT_BITSETS;
 
 	ethnl_init_reply_data(reply_data, ops, dev);