hwrng: timeriomem - Remove 'max < 4' condition check

In read routiene max is always >= 4. The check whether 'max < 4' is not
necessary. Remove it.

Signed-off-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
Acked-By: Rick Altherr <raltherr@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>