driver core: Avoid NULL pointer dereferences in device_is_bound()

If device_is_bound() is called on a device that's not been registered
yet, it will attepmt to dereference dev->p which is NULL, so avoid
that by checking dev->p in there against NULL.

Fixes: 6b9cb427 "device core: add device_is_bound()"
Reported-and-tested-by: NGuenter Roeck <linux@roeck-us.net>
Tested-by: NTony Lindgren <tony@atomide.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/base/dd.c

@@ -234,7 +234,7 @@ late_initcall(deferred_probe_initcall);
  */
 bool device_is_bound(struct device *dev)
 {
-	return klist_node_attached(&dev->p->knode_driver);
+	return dev->p && klist_node_attached(&dev->p->knode_driver);
 }
 
 static void driver_bound(struct device *dev)