We need limits.h for PATH_MAX, fixes:

tc_bpf.c: In function ‘bpf_map_selfcheck_pinned’:
tc_bpf.c:222:12: error: ‘PATH_MAX’ undeclared (first use in this
function)
  char file[PATH_MAX], buff[4096];
Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>