crypto: sun4i-ss - enable pm_runtime

This patch enables power management on the Security System.
sun4i-ss now depends on PM because it simplify code and prevent some ifdef.
But this is not a problem since arch maintainer want ARCH_SUNXI to
depend on PM in the future.

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>