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

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: a5a0a39f60e4 ("netlink: add net device refcount tracker to struct ethnl_req_info")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Johannes Berg <johannes@sipsolutions.net>
Tested-by: Johannes Berg <johannes@sipsolutions.net>
Link: https://lore.kernel.org/r/20220105170849.2610470-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>