[TCP]: Move LOSTRETRANS MIB outside !(L|S) check

Usually those skbs will have L set, not counting them as lost
retransmissions is misleading.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>