NTB: fix possible name leak in ntb_register_device()

In the Linux kernel, the following vulnerability has been resolved: NTB: fix possible name leak in ntb_register_device() If device_register() fails in ntb_register_device(), the device name allocated by dev_set_name() should be freed. As per the comment in device_register(), callers should use put_device() to give up the reference in the error path. So fix this by calling put_device() in the error path so that the name can be freed in kobject_cleanup(). As a result of this, put_device() in the error path of ntb_register_device() is removed and the actual error is returned. [mani: reworded commit message]