rename nvme_ctrlr_destroy_qpair to nvme_ctrlr_destroy_qpairs

[hordijk_netapp.com]

Summary

Maintain symmetry with nvme_ctrlr_create_qpairs, making it easier to match
init/uninit scenarios. nvme_ctrlr_create_qpairs creates all qpairs in a single
function call. nvme_ctrlr_destroy_qpairs will now do the same.

This also enables a future change where we can have different CQ/SQ qpair
configurations.

Signed-off-by: John Meneghini <[e-mail]>

[hordijk_netapp.com]

Updating commit description.

[imp]

This change looks correct to me. Unsure why we need to do it though. Would like to see the follow-on fixes that this depends on, since I'm pretty happy with this if there's some reason to change.