[IPSEC]: Move integrity stat collection into xfrm_input

Similar to the moving out of the replay processing on the output, this
patch moves the integrity stat collectin from x->type->input into
xfrm_input.

This would eventually allow transforms such as AH/ESP to be lockless.

The error value EBADMSG (currently unused in the crypto layer) is used
to indicate a failed integrity check.  In future this error can be
directly returned by the crypto layer once we switch to aead
algorithms.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/ah6.c b/net/ipv6/ah6.c
index 4eaf550..d4b59ec 100644
--- a/net/ipv6/ah6.c
+++ b/net/ipv6/ah6.c
@@ -379,10 +379,9 @@
 		err = ah_mac_digest(ahp, skb, ah->auth_data);
 		if (err)
 			goto free_out;
-		err = -EINVAL;
 		if (memcmp(ahp->work_icv, auth_data, ahp->icv_trunc_len)) {
 			LIMIT_NETDEBUG(KERN_WARNING "ipsec ah authentication error\n");
-			x->stats.integrity_failed++;
+			err = -EBADMSG;
 			goto free_out;
 		}
 	}