nvme: remove redundant status mask

In nvme_get_error_status_str(), the status code is already masked
with 0x7ff at the beginning of the function.
Don't bother masking it again when indexing nvme_statuses.

Signed-off-by: Caleb Sander <csander@purestorage.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Keith Busch <kbusch@kernel.org>