driver core: remove unnecessary function extern declare

device_private_init is called only in core.c, extern declare is
unnecessary and make it static.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/base.h

@@ -84,8 +84,6 @@ struct device_private {
 #define to_device_private_bus(obj)	\
 	container_of(obj, struct device_private, knode_bus)
 
-extern int device_private_init(struct device *dev);
-
 /* initialisation functions */
 extern int devices_init(void);
 extern int buses_init(void);

drivers/base/core.c

@@ -1736,7 +1736,7 @@ static void device_remove_sys_dev_entry(struct device *dev)
 	}
 }
 
-int device_private_init(struct device *dev)
+static int device_private_init(struct device *dev)
 {
 	dev->p = kzalloc(sizeof(*dev->p), GFP_KERNEL);
 	if (!dev->p)