crypto: drbg - select SHA512

With the swtich to use HMAC(SHA-512) as the default DRBG type, the
configuration must now also select SHA-512.

Fixes: 9b7b9468

 "crypto: DRBG - switch to HMAC SHA512 DRBG as default
DRBG"
Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Signed-off-by: Stephan Mueller <smueller@chronox.com>
Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>