crypto: sun8i-ss - Use helper to set reqsize

The value of reqsize must only be changed through the helper.

Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>