RDMA/siw: Remove namespace check from siw_netdev_event()

syzbot is reporting that siw_netdev_event(NETDEV_UNREGISTER) cannot destroy
siw_device created after unshare(CLONE_NEWNET) due to net namespace check.
It seems that this check was by error there and should be removed.
Reported-by: syzbot <syzbot+5e70d01ee8985ae62a3b@syzkaller.appspotmail.com>
Link: https://syzkaller.appspot.com/bug?extid=5e70d01ee8985ae62a3bSuggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Suggested-by: Leon Romanovsky <leon@kernel.org>
Fixes: bdcf26bf ("rdma/siw: network and RDMA core interface")
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Link: https://lore.kernel.org/r/a44e9ac5-44e2-d575-9e30-02483cc7ffd1@I-love.SAKURA.ne.jpReviewed-by: Bernard Metzler <bmt@zurich.ibm.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>

drivers/infiniband/sw/siw/siw_main.c

@@ -437,9 +437,6 @@ static int siw_netdev_event(struct notifier_block *nb, unsigned long event,
 
 	dev_dbg(&netdev->dev, "siw: event %lu\n", event);
 
-	if (dev_net(netdev) != &init_net)
-		return NOTIFY_OK;
-
 	base_dev = ib_device_get_by_netdev(netdev, RDMA_DRIVER_SIW);
 	if (!base_dev)
 		return NOTIFY_OK;