ACPI / PM: Fix header of acpi_dev_pm_detach() in acpi.h

The header of acpi_dev_pm_detach() in include/linux/acpi.h has an
incorrect return type, which should be void.  Fix that.
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

include/linux/acpi.h

@@ -459,7 +459,7 @@ static inline int acpi_subsys_resume_early(struct device *dev) { return 0; }
 
 #if defined(CONFIG_ACPI) && defined(CONFIG_PM)
 int acpi_dev_pm_attach(struct device *dev, bool power_on);
-int acpi_dev_pm_detach(struct device *dev, bool power_off);
+void acpi_dev_pm_detach(struct device *dev, bool power_off);
 #else
 static inline int acpi_dev_pm_attach(struct device *dev, bool power_on)
 {