nvme: Check for Security send/recv support before issuing commands.

We need to verify that the controller supports the security
commands before actually trying to issue them.

Signed-off-by: Scott Bauer <scott.bauer@intel.com>
[hch: moved the check so that we don't call into the OPAL code if not
      supported]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>