fix(icmp): fixed compilation on AIX

plugins-root/check_icmp.c

@@ -1274,9 +1274,7 @@ static int recvfrom_wto(int sock, void *buf, unsigned int len,
   char ans_data[4096];
   struct msghdr hdr;
   struct iovec iov;
-#ifdef SO_TIMESTAMP
   struct cmsghdr *chdr;
-#endif
 
   if (!*timo) {
     if (debug)