Update the crypto_simd module to support wrapping AEAD algorithms.
Previously it only supported skciphers.  The code for each is similar.

I'll be converting the x86 implementations of AES-GCM, AEGIS, and MORUS
to use this.  Currently they each independently implement the same
functionality.  This will not only simplify the code, but it will also
fix the bug detected by the improved self-tests: the user-provided
aead_request is modified.  This is because these algorithms currently
reuse the original request, whereas the crypto_simd helpers build a new
request in the original request's context.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>