netlink/route: Fix the argument list for rtnl_handle_iflink()

This function is registered as a ifnet_link_event and so should have the
corresponding argument list.

PR: 282870
Reported by: nakayamakenjiro@gmail.com
MFC after: 1 week

(cherry picked from commit 0289db3259532d51ebe58bc0b2647a0d9e6cae66)