selinux: use native iterator types

selinux: use native iterator types

Use types for iterators equal to the type of the to be compared values.

Reported by clang:

    ../ss/sidtab.c:126:2: warning: comparison of integers of different
                          signs: 'int' and 'unsigned long'
      126 |  hash_for_each_rcu(sidtab->context_to_sid, i, entry, list) {
          |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    ../hashtable.h:139:51: note: expanded from macro 'hash_for_each_rcu'
      139 |  for (... ; obj == NULL && (bkt) < HASH_SIZE(name);\
          |                             ~~~  ^ ~~~~~~~~~~~~~~~

    ../selinuxfs.c:1520:23: warning: comparison of integers of different
                            signs: 'int' and 'unsigned int'
     1520 |  for (cpu = *idx; cpu < nr_cpu_ids; ++cpu) {
          |                   ~~~ ^ ~~~~~~~~~~

    ../hooks.c:412:16: warning: comparison of integers of different signs:
                       'int' and 'unsigned long'
      412 |  for (i = 0; i < ARRAY_SIZE(tokens); i++) {
          |              ~ ^ ~~~~~~~~~~~~~~~~~~

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
[PM: munged the clang output due to line length concerns]
Signed-off-by: Paul Moore <paul@paul-moore.com>