commit a5596d63 upstream.

This patch adds a way for ahash users to determine whether a key
is required by a crypto_ahash transform.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>