xfrm: policy: fix policy hash rebuild

xfrm: policy: fix policy hash rebuild

Dan Carpenter reports following static checker warning:
 net/xfrm/xfrm_policy.c:1316 xfrm_hash_rebuild()
 warn: 'dir' is out of bounds '3' vs '2'

 |  1280          /* reset the bydst and inexact table in all directions */
 |  1281          xfrm_hash_reset_inexact_table(net);
 |  1282
 |  1283          for (dir = 0; dir < XFRM_POLICY_MAX; dir++) {
 |                              ^^^^^^^^^^^^^^^^^^^^^
 |dir == XFRM_POLICY_MAX at the end of this loop.
 |  1304          /* re-insert all policies by order of creation */
 |  1305          list_for_each_entry_reverse(policy, &net->xfrm.policy_all, walk.all) {
 [..]
 |  1314                                            xfrm_policy_id2dir(policy->index));
 |  1315                  if (!chain) {
 |  1316                          void *p = xfrm_policy_inexact_insert(policy, dir, 0);

Fix this by updating 'dir' based on current policy.  Otherwise, the
inexact policies won't be found anymore during lookup, as they get
hashed to a bogus bin.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: cc1bb845adc9 ("xfrm: policy: return NULL when inexact search needed")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>