crypto: drbg - update FIPS CTR self-checks to aes256

When originally drbg was introduced FIPS self-checks for all types but
CTR were using the most preferred parameters for each type of
DRBG. Update CTR self-check to use aes256.

This patch updates code from 541af946 ("crypto: drbg - SP800-90A
Deterministic Random Bit Generator"), but is not interesting to
cherry-pick for stable updates, because it doesn't affect regular
builds, nor has any tangible effect on FIPS certifcation.

Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
Reviewed-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>