ARM: EXYNOS: Kill exynos_pm_late_initcall()

The only thing exynos_pm_late_initcall() does is calling
pm_genpd_poweroff_unused(), which is already stubbed when
CONFIG_PM_GENERIC_DOMAINS is not enabled. So replace
exynos_pm_late_initcall() with a direct call to
pm_genpd_poweroff_unused().

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>