nvme: don't overwrite req->cmd_flags on sync cmd

In __nvme_submit_sync_cmd, the request direction is overwritten when
the REQ_FAILFAST_DRIVER flag is set.

Signed-off-by: Matias Bjørling <m@bjorling.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Fixes: 75619bfa ("NVMe: End sync requests immediately on failure")
Signed-off-by: Jens Axboe <axboe@fb.com>