crypto: drbg - Change DRBG_MAX_REQUESTS to 4096

crypto: drbg - Change DRBG_MAX_REQUESTS to 4096

Currently a formal reseed happens only after each 1048576 requests.

That's quite a high number.  Let's follow the example of BoringSSL and
use a more conservative value of 4096.

Note that in practice this makes little difference, now that we're
including 32 bytes from get_random_bytes() in the additional input on
every request anyway, which is a de facto reseed.

But for the same reason, we might as well decrease the actual reseed
interval to something more reasonable.

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