[ Upstream commit 100c815cbd56480b3e31518475b04719c363614a ]

If we can't get a namespace don't leak the SRCU lock.  nvme_ioctl was
working around this, but nvme_pr_command wasn't handling this properly.
Just do what callers would usually expect.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NKeith Busch <keith.busch@intel.com>
Reviewed-by: NChaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>