crypto: cipher - Add crypto_clone_cipher

Allow simple ciphers to be cloned, if they don't have a cra_init
function. This basically rules out those ciphers that require a
fallback.

In future simple ciphers will be eliminated, and replaced with a
linear skcipher interface. When that happens this restriction will
disappear.

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

crypto: remove cipher routines from public crypto API

The cipher routines in the crypto API are mostly intended for templates
implementing skcipher modes generically in software, and shouldn't be
used outside of the crypto subsystem. So move the prototypes and all
related definitions to a new header file under include/crypto/internal.
Also, let's use the new module namespace feature to move the symbol
exports into a new namespace CRYPTO_INTERNAL.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>