[CRYPTO] tcrypt: Add aead support

Add AEAD support to tcrypt, needed by GCM.

Signed-off-by: Mikko Herranen <mh1@iki.fi>
Reviewed-by: Mika Kukkonen <mika.kukkonen@nsn.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>