PM / core: Drop internal unused inline functions for wakeups

The inline versions of device_wakeup_arm|disarm_wake_irqs(), which are
available while when CONFIG_PM is set and CONFIG_PM_SLEEP unset, are not
being used, hence let's drop them.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>