carl9170 firmware tools: fix compile errors in wol.c

wol.c: In function ‘monitor_init’:
wol.c:40:19: warning: implicit declaration of function ‘if_nametoindex’
  ll.sll_ifindex = if_nametoindex(ifname);
                   ^
wol.c:46:45: warning: implicit declaration of function ‘htons’
  monitor_sock = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
                                             ^

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>