ip: code shrink

ip: code shrink

function                                             old     new   delta
do_ipaddr                                             78      81      +3
do_iprule                                            140     139      -1
do_iptunnel                                          283     278      -5
iprule_modify                                        851     841     -10
ipaddr_modify                                       1293    1236     -57
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/4 up/down: 3/-73)             Total: -70 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>