PM: domains: Rename pm_genpd_syscore_poweroff|poweron()

To better describe what the pm_genpd_syscore_poweroff|poweron() functions
actually do, let's rename them to dev_pm_genpd_suspend|resume() and update
the rather few callers of them accordingly (a couple of clocksource
drivers).

Moreover, let's take the opportunity to add some documentation of these
exported functions, as that is currently missing.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/drivers/clocksource/sh_mtu2.c b/drivers/clocksource/sh_mtu2.c
index bfccb31..169a1fc 100644
--- a/drivers/clocksource/sh_mtu2.c
+++ b/drivers/clocksource/sh_mtu2.c
@@ -297,12 +297,12 @@ static int sh_mtu2_clock_event_set_periodic(struct clock_event_device *ced)
 
 static void sh_mtu2_clock_event_suspend(struct clock_event_device *ced)
 {
-	pm_genpd_syscore_poweroff(&ced_to_sh_mtu2(ced)->mtu->pdev->dev);
+	dev_pm_genpd_suspend(&ced_to_sh_mtu2(ced)->mtu->pdev->dev);
 }
 
 static void sh_mtu2_clock_event_resume(struct clock_event_device *ced)
 {
-	pm_genpd_syscore_poweron(&ced_to_sh_mtu2(ced)->mtu->pdev->dev);
+	dev_pm_genpd_resume(&ced_to_sh_mtu2(ced)->mtu->pdev->dev);
 }
 
 static void sh_mtu2_register_clockevent(struct sh_mtu2_channel *ch,