crypto: nx - remove stale comment referring to the blkcipher walk API

These drivers do not use either the deprecated blkcipher or the current
skcipher walk API, so this comment must refer to a previous state of the
driver that no longer exists. So drop the comments.

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