xfrm: Use __skb_queue_tail in xfrm_trans_queue

We do not need locking in xfrm_trans_queue because it is designed
to use per-CPU buffers.  However, the original code incorrectly
used skb_queue_tail which takes the lock.  This patch switches
it to __skb_queue_tail instead.

Reported-and-tested-by: Artem Savkov <asavkov@redhat.com>
Fixes: acf568ee ("xfrm: Reinject transport-mode packets...")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>