Merge branch 'net-Move-fib_nh-and-fib6_nh-to-a-common-struct'

David Ahern says:

====================
net: Move fib_nh and fib6_nh to a common struct

First set of three with the end goal of enabling IPv6 gateways with IPv4
routes.

This set refactors ipv4 and ipv6 code to create init and release
helpers for each protocol and moving common elements to a fib_nh_common
struct.

v3
- split the reject setting into 2 with helper to the checks. This
  avoids changing cfg->fc_flags in fib6_nh_init

v2
- addressed Ido's comments: cleanup on failure path in nh_init helpers,
  ordering in fib6_nh_release, and removal of RTF_GATEWAY from fib6_info
  uses in mlxsw
====================

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