crypto: ahash - Add crypto_ahash_tested() helper function

Add a little inline helper function
    crypto_ahash_tested()
to the internal/hash.h header file to retrieve the tested
status (that is the CRYPTO_ALG_TESTED bit in the cra_flags).

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Suggested-by: Herbert Xu <herbert@gondor.apana.org.au>
Reviewed-by: Holger Dengler <dengler@linux.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>