crypto: sun4i-ss - simplify enable/disable of the device

This patch regroups resource enabling/disabling in dedicated function.
This simplify error handling and will permit to support power
management.

Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>