xfrm: Move IPsec replay detection functions to a separate file
To support multiple versions of replay detection, we move the replay
detection functions to a separate file and make them accessible
via function pointers contained in the struct xfrm_replay.
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com> Acked-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>