libiproute: code shrink by adding FAST_FUNC

libiproute: code shrink by adding FAST_FUNC

function                                             old     new   delta
ipaddr_list_or_flush                                1282    1293     +11
ip_parse_common_args                                 153     151      -2
ip_main                                               53      50      -3
ip_do                                                 19      15      -4
do_iptunnel                                          985     980      -5
do_iprule                                            982     977      -5
do_iplink                                           1637    1631      -6
do_iproute                                          2105    2098      -7
do_ipaddr                                           1406    1398      -8
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/8 up/down: 11/-40)            Total: -29 bytes

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