power: supply: Provide stubs for charge_behaviour helpers

When CONFIG_SYSFS is not enabled provide stubs for the helper functions
to not break their callers.

Fixes: 539b9c94ac ("power: supply: add helpers for charge_behaviour sysfs")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/r/20220108153158.189489-1-linux@weissschuh.net
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

include/linux/power_supply.h

@@ -553,6 +553,21 @@ ssize_t power_supply_charge_behaviour_show(struct device *dev,
 					   char *buf);
 
 int power_supply_charge_behaviour_parse(unsigned int available_behaviours, const char *buf);
+#else
+static inline
+ssize_t power_supply_charge_behaviour_show(struct device *dev,
+					   unsigned int available_behaviours,
+					   enum power_supply_charge_behaviour behaviour,
+					   char *buf)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int power_supply_charge_behaviour_parse(unsigned int available_behaviours,
+						      const char *buf)
+{
+	return -EOPNOTSUPP;
+}
 #endif
 
 #endif /* __LINUX_POWER_SUPPLY_H__ */