nvme-pci: Fix queue double allocations

The queue count says the highest queue that's been allocated, so don't
reallocate a queue lower than that.

Fixes: 147b27e4

 ("nvme-pci: allocate device queues storage space at probe")
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>