libnetlink: code shrink

libnetlink: code shrink

function                                             old     new   delta
xrtnl_open                                            95      93      -2
parse_rtattr                                          87      85      -2
rtnl_close                                             9       -      -9
xrtnl_wilddump_request                               101      64     -37
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(add/remove: 0/1 grow/shrink: 0/3 up/down: 0/-50)             Total: -50 bytes

Signed-off-by: Natanael Copa <natanael.copa@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>