extcon: Add stubs for extcon_register_notifier_all() functions

Add stubs for extcon_register_notifier_all() function for !CONFIG_EXTCON
case. This is useful for compile testing and for drivers which use
EXTCON but do not require it (therefore do not depend on CONFIG_EXTCON).

Fixes: 815429b39d94 ("extcon: Add new extcon_register_notifier_all() to monitor all external connectors")
Reported-by: kernel test robot <[e-mail]>
Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Chanwoo Choi <[e-mail]>

include/linux/extcon.h

···
 				struct extcon_dev *edev, unsigned int id,
 				struct notifier_block *nb) { }
 
+static inline int extcon_register_notifier_all(struct extcon_dev *edev,
+					       struct notifier_block *nb)
+{
+	return 0;
+}
+
+static inline int extcon_unregister_notifier_all(struct extcon_dev *edev,
+						 struct notifier_block *nb)
+{
+	return 0;
+}
+
+static inline int devm_extcon_register_notifier_all(struct device *dev,
+						    struct extcon_dev *edev,
+						    struct notifier_block *nb)
+{
+	return 0;
+}
+
+static inline void devm_extcon_unregister_notifier_all(struct device *dev,
+						       struct extcon_dev *edev,
+						       struct notifier_block *nb) { }
+
 static inline struct extcon_dev *extcon_get_extcon_dev(const char *extcon_name)
 {
 	return ERR_PTR(-ENODEV);