crypto: drbg - De-virtualize drbg_state_ops

crypto: drbg - De-virtualize drbg_state_ops

Now that there's only one set of state operations, use direct calls to
those operations.

No change in behavior.  In particular, drbg_alloc_state() doesn't change
behavior, because the only remaining drbg_core uses HMAC_DRBG.
drbg_uninstantiate() doesn't change behavior, because a NULL d_ops
implied NULL priv_data which makes a drbg_fini_hash_kernel() a no-op.

Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>