ipvlan: Fix dependency issue

kbuild-build-bot reported that if NETFILTER is not selected, the
build fails pointing to netfilter symbols.

Fixes: 4fbae7d8

 ("ipvlan: Introduce l3s mode")

Signed-off-by: Mahesh Bandewar <maheshb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>