esp4: Fix integrity verification when ESN are used

commit 7c7fedd5 upstream.

When handling inbound packets, the two halves of the sequence number
stored on the skb are already in network order.

Fixes: 7021b2e1 ("esp4: Switch to new AEAD interface")
Signed-off-by: Tobias Brunner <tobias@strongswan.org>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>