pflog: Include <limits.h> for UINT_MAX

pflog: Include <limits.h> for UINT_MAX

This change avoids an error with illumos.

The error was:

print-pflog.c: In function 'pflog_print':
print-pflog.c:254:37: error: 'UINT_MAX' undeclared (first use in this
  function)
  254 |         if (GET_BE_U_4(hdr->uid) != UINT_MAX)
      |                                     ^~~~~~~~
print-pflog.c:32:1: note: 'UINT_MAX' is defined in header '<limits.h>';
  did you forget to '#include <limits.h>'?