PM: Make ACPI wakeup from S5 work again when CONFIG_PM_SLEEP is unset

Commit 074037ec (PM / Wakeup: Introduce wakeup source objects and
event statistics (v3)) caused ACPI wakeup to only work if
CONFIG_PM_SLEEP is set, but it also worked for CONFIG_PM_SLEEP unset
before.  This can be fixed by making device_set_wakeup_enable(),
device_init_wakeup() and device_may_wakeup() work in the same way
as before commit 074037ec when CONFIG_PM_SLEEP is unset.
Reported-and-tested-by: Justin Maggard <jmaggard10@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

include/linux/pm.h

@@ -431,6 +431,8 @@ struct dev_pm_info {
 	struct list_head	entry;
 	struct completion	completion;
 	struct wakeup_source	*wakeup;
+#else
+	unsigned int		should_wakeup:1;
 #endif
 #ifdef CONFIG_PM_RUNTIME
 	struct timer_list	suspend_timer;

include/linux/pm_wakeup.h

@@ -109,11 +109,6 @@ static inline bool device_can_wakeup(struct device *dev)
 	return dev->power.can_wakeup;
 }
 
-static inline bool device_may_wakeup(struct device *dev)
-{
-	return false;
-}
-
 static inline struct wakeup_source *wakeup_source_create(const char *name)
 {
 	return NULL;
@@ -134,24 +129,32 @@ static inline void wakeup_source_unregister(struct wakeup_source *ws) {}
 
 static inline int device_wakeup_enable(struct device *dev)
 {
-	return -EINVAL;
+	dev->power.should_wakeup = true;
+	return 0;
 }
 
 static inline int device_wakeup_disable(struct device *dev)
 {
+	dev->power.should_wakeup = false;
 	return 0;
 }
 
-static inline int device_init_wakeup(struct device *dev, bool val)
+static inline int device_set_wakeup_enable(struct device *dev, bool enable)
 {
-	dev->power.can_wakeup = val;
-	return val ? -EINVAL : 0;
+	dev->power.should_wakeup = enable;
+	return 0;
 }
 
+static inline int device_init_wakeup(struct device *dev, bool val)
+{
+	device_set_wakeup_capable(dev, val);
+	device_set_wakeup_enable(dev, val);
+	return 0;
+}
 
-static inline int device_set_wakeup_enable(struct device *dev, bool enable)
+static inline bool device_may_wakeup(struct device *dev)
 {
-	return -EINVAL;
+	return dev->power.can_wakeup && dev->power.should_wakeup;
 }
 
 static inline void __pm_stay_awake(struct wakeup_source *ws) {}