nvme: restrict management ioctls to admin

The passthrough commands already have this restriction, but the other
operations do not. Require the same capabilities for all users as all of
these operations, which include resets and rescans, can be disruptive.

Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>