crypto: algif_aead - Switch to new AEAD interface

This patch makes use of the new AEAD interface which uses a single
SG list instead of separate lists for the AD and plain text.

Note that the user-space interface now requires both input and
output to be of the same length, and both must include space for
the AD as well as the authentication tag.

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