nvme-pci: refactor the tagset handling in nvme_reset_work

nvme-pci: refactor the tagset handling in nvme_reset_work

The code to create, update or delete a tagset and namespaces in
nvme_reset_work is a bit convoluted.  Refactor it with a two high-level
conditionals for first probe vs reset and I/O queues vs no I/O queues
to make the code flow more clear.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20221101150050.3510-3-hch@lst.de
[axboe: fix whitespace issue]
Signed-off-by: Jens Axboe <axboe@kernel.dk>