Now that the tfm is passed directly to setkey instead of the ctx, we no
longer need to pass the &tfm->crt_flags pointer.

This patch also gets rid of a few unnecessary checks on the key length
for ciphers as the cipher layer guarantees that the key length is within
the bounds specified by the algorithm.

Rather than testing dia_setkey every time, this patch does it only once
during crypto_alloc_tfm.  The redundant check from crypto_digest_setkey
is also removed.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>