kernel: ipvlan: Fix use-after-free in ipvlan_get_iflink().

In the Linux kernel, the following vulnerability has been resolved: ipvlan: Fix use-after-free in ipvlangetiflink. syzbot presented an use-after-free report 0 regarding ipvlan and linkwatch. ipvlan does not hold a refcnt of the lower device unlike vlan and macvlan. If the linkwatch work is...