crypto: seqiv - Do not use req->iv after crypto_aead_encrypt

crypto: seqiv - Do not use req->iv after crypto_aead_encrypt

As soon as crypto_aead_encrypt is called, the underlying request
may be freed by an asynchronous completion.  Thus dereferencing
req->iv after it returns is invalid.

Instead of checking req->iv against info, create a new variable
unaligned_info and use it for that purpose instead.

Fixes: 0a270321dbf9 ("[CRYPTO] seqiv: Add Sequence Number IV Generator")
Reported-by: Xiumei Mu <xmu@redhat.com>
Reported-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>