[XFRM]: Fix statistics.

o Outbound sequence number overflow error status
  is counted as XfrmOutStateSeqError.
o Additionaly, it changes inbound sequence number replay
  error name from XfrmInSeqOutOfWindow to XfrmInStateSeqError
  to apply name scheme above.
o Inbound IPv4 UDP encapsuling type mismatch error is wrongly
  mapped to XfrmInStateInvalid then this patch fiex the error
  to XfrmInStateMismatch.

Signed-off-by: Masahide NAKAMURA <nakam@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/xfrm/xfrm_output.c b/net/xfrm/xfrm_output.c
index f4a1047..fc69036 100644
--- a/net/xfrm/xfrm_output.c
+++ b/net/xfrm/xfrm_output.c
@@ -64,6 +64,7 @@
 		if (x->type->flags & XFRM_TYPE_REPLAY_PROT) {
 			XFRM_SKB_CB(skb)->seq = ++x->replay.oseq;
 			if (unlikely(x->replay.oseq == 0)) {
+				XFRM_INC_STATS(LINUX_MIB_XFRMOUTSTATESEQERROR);
 				x->replay.oseq--;
 				xfrm_audit_state_replay_overflow(x, skb);
 				err = -EOVERFLOW;