[NETNS]: FIB rules API cleanup.

[NETNS]: FIB rules API cleanup.

Remove struct net from fib_rules_register(unregister)/notify_change
paths and diet code size a bit.

add/remove: 0/0 grow/shrink: 10/12 up/down: 35/-100 (-65)
function                                     old     new   delta
notify_rule_change                           273     280      +7
trie_show_stats                              471     475      +4
fn_trie_delete                               473     477      +4
fib_rules_unregister                         144     148      +4
fib4_rule_compare                            119     123      +4
resize                                      2842    2845      +3
fn_trie_select_default                       515     518      +3
inet_sk_rebuild_header                       836     838      +2
fib_trie_seq_show                            764     766      +2
__devinet_sysctl_register                    276     278      +2
fn_trie_lookup                              1124    1123      -1
ip_fib_check_default                         133     131      -2
devinet_conf_sysctl                          223     221      -2
snmp_fold_field                              126     123      -3
fn_trie_insert                              2091    2086      -5
inet_create                                  876     870      -6
fib4_rules_init                              197     191      -6
fib_sync_down                                452     444      -8
inet_gso_send_check                          334     325      -9
fib_create_info                             3003    2991     -12
fib_nl_delrule                               568     553     -15
fib_nl_newrule                               883     852     -31

Signed-off-by: Denis V. Lunev <den@openvz.org>
Acked-by: Daniel Lezcano <dlezcano@fr.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>