The IOC_PR_CLEAR and IOC_PR_RELEASE ioctls are
non-functional on NVMe devices because the nvme_pr_clear()
and nvme_pr_release() functions set the IEKEY field incorrectly.
The IEKEY field should be set only when the key is zero (i.e,
not specified).  The current code does it backwards.

Furthermore, the NVMe spec describes the persistent
reservation "clear" function as an option on the reservation
release command. The current implementation of nvme_pr_clear()
erroneously uses the reservation register command.

Fix these errors. Note that NVMe version 1.3 and later specify
that setting the IEKEY field will return an error of Invalid
Field in Command.  The fix will set IEKEY when the key is zero,
which is appropriate as these ioctls consider a zero key to
be "unspecified", and the intention of the spec change is
to require a valid key.

Tested on a version 1.4 PCI NVMe device in an Azure VM.

Fixes: 1673f1f0 ("nvme: move block_device_operations and ns/ctrl freeing to common code")
Fixes: 1d277a63 ("NVMe: Add persistent reservation ops")
Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>