power: supply: core: unexport power_supply_property_is_writeable()

Since commit ("power: supply: Drop use_cnt check from power_supply_property_is_writeable()"),
this function does not check use_cnt anymore, making it unsuitable for
general usage. As it is only used by the psy core anyways, remove it
from the public header and unexport it to avoid misusage.

Signed-off-by: Thomas Weißschuh <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Sebastian Reichel <[e-mail]>

drivers/power/supply/power_supply.h

···
 struct device_type;
 struct power_supply;
 
+extern int power_supply_property_is_writeable(struct power_supply *psy,
+					      enum power_supply_property psp);
+
 #ifdef CONFIG_SYSFS
 
 extern void power_supply_init_attrs(void);

drivers/power/supply/power_supply_core.c

···
 {
 	return psy->desc->property_is_writeable && psy->desc->property_is_writeable(psy, psp);
 }
-EXPORT_SYMBOL_GPL(power_supply_property_is_writeable);
 
 void power_supply_external_power_changed(struct power_supply *psy)
 {

drivers/power/supply/power_supply_hwmon.c

···
 #include <linux/hwmon.h>
 #include <linux/power_supply.h>
 #include <linux/slab.h>
+#include "power_supply.h"
 
 struct power_supply_hwmon {
 	struct power_supply *psy;

include/linux/power_supply.h

···
 			    const union power_supply_propval *val)
 { return 0; }
 #endif
-extern int power_supply_property_is_writeable(struct power_supply *psy,
-					enum power_supply_property psp);
 extern void power_supply_external_power_changed(struct power_supply *psy);
 
 extern struct power_supply *__must_check