hwrng: exynos - add CONFIG_PM_SLEEP/CONFIG_PM_RUNTIME to suspend/resume

This patch adds CONFIG_PM_SLEEP to suspend/resume functions to fix
the following build warning when CONFIG_PM_SLEEP is not selected.

drivers/char/hw_random/exynos-rng.c:147:12: warning: 'exynos_rng_runtime_suspend' defined but not used [-Wunused-function]
drivers/char/hw_random/exynos-rng.c:157:12: warning: 'exynos_rng_runtime_resume' defined but not used [-Wunused-function]

Add CONFIG_PM_RUNTIME to suspend/resume functions to fix the build
error. It is because UNIVERSAL_DEV_PM_OPS macro is related to both
CONFIG_PM_SLEEP and CONFIG_PM_RUNTIME.

drivers/char/hw_random/exynos-rng.c:167:8: error: 'exynos_rng_runtime_suspend' undeclared here (not in a function)
drivers/char/hw_random/exynos-rng.c:167:8: error: 'exynos_rng_runtime_resume' undeclared here (not in a function)

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Reported-by: David Rientjes <rientjes@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>