crypto: ux500/hash - Silence compiler warning for !CONFIG_PM

The system PM functions were unused when CONFIG_PM is unset. Let's move
them inside CONFIG_PM_SLEEP to silence the compiler warning.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>