kset: convert struct bus_device->drivers to use kset_create

Dynamically create the kset instead of declaring it statically.

Having 3 static kobjects in one structure is not only foolish, but ripe
for nasty race conditions if handled improperly.  We also rename the
field to catch any potential users of it (not that there should be
outside of the driver core...)

Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/base/driver.c

@@ -185,7 +185,7 @@ void driver_unregister(struct device_driver * drv)
  */
 struct device_driver *driver_find(const char *name, struct bus_type *bus)
 {
-	struct kobject *k = kset_find_obj(&bus->drivers, name);
+	struct kobject *k = kset_find_obj(bus->drivers_kset, name);
 	if (k)
 		return to_drv(k);
 	return NULL;