[CRYPTO] eseqiv: Fix off-by-one encryption

After attaching the IV to the head during encryption, eseqiv does not
increase the encryption length by that amount.  As such the last block
of the actual plain text will be left unencrypted.

Fortunately the only user of this code hifn currently crashes so this
shouldn't affect anyone :)

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>