Merge branch 'net-wean-netfilter-from-fib_nh'

David Ahern says:

====================
net: wean netfilter from fib_nh

Two netfilter modules reference fib_nh. In both cases the code is
only checking if a nexthop in a fib_info uses a specific device.
Both instances essentially duplicate code from __fib_validate_source,
so move that code into a helper and flip the netfilter modules to
use it.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>