nvme-pci: fix dma mapping leak on data setup error

nvme-pci: fix dma mapping leak on data setup error

We're leaking the initial DMA mapping during iteration if we fail to
allocate the tracking descriptor for both PRP and SGL. Unmap the
iterator directly; we can't use the existing unmap helper because it
depends on the tracking descriptor being successfully allocated, so a
new one for an in-use iterator is provided.

The mappings were also leaking when the driver detects an invalid
bio_vec when mapping PRPs, so fix that too.

Fixes: b8b7570a7ec87 ("nvme-pci: fix dma unmapping when using PRPs and not using the IOVA mapping")
Fixes: 7ce3c1dd78fca ("nvme-pci: convert the data mapping to blk_rq_dma_map")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>