[ Upstream commit bf00f5426074249058a106a6edbb89e4b25a4d79 ] The class is set in mISDN_register_device(), but if device_add() returns error, it will lead to delete a device without added, fix this by using device_is_registered() to check if the device is registered. Fixes: a900845e5661 ("mISDN: Add support for Traverse Technologies NETJet PCI cards") Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <sashal@kernel.org>