ipv4: remove ipv4_ifdown_dst from route.c
ipv4: remove ipv4_ifdown_dst from route.c

ipv4_ifdown_dst does nothing after IPv4 route caches removal,
so we can remove it.

Signed-off-by: Li RongQing <81c2f95e9d1350da984a3ef03e964ca9a6cbc5c2@gmail.com>
Signed-off-by: David S. Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs