If a device is providing a single IRQ vector, the IO queue will share
that vector with the admin queue. This is an unmanaged vector, so does
not have a valid PCI IRQ affinity. Avoid trying to extract a managed
affinity in this case and let blk-mq set up the cpu:queue mapping instead.
Otherwise we'd hit the following warning when the device is using MSI:
Fixes: 22b5560195bd6 ("nvme-pci: Separate IO and admin queue IRQ vectors") Reported-by: Iván Chavero <ichavero@chavero.com.mx> Reviewed-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Keith Busch <keith.busch@intel.com>