commit a1383cd8 upstream.

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