driver: ipvlan: Fix one possible memleak in ipvlan_link_new

When ipvlan_link_new fails and creates one ipvlan port, it does not
destroy the ipvlan port created. It causes mem leak and the physical
device contains invalid ipvlan data.

Signed-off-by: Gao Feng <fgao@ikuai8.com>
Signed-off-by: David S. Miller <davem@davemloft.net>