nvme: fix drvdata setup for the nvme device

Pass the right private data to device_create_with_groups from the
beginning, and remove the superflous call to dev_set_drvdata.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jon Derrick <jonathan.derrick@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>