nvme: Split the namespace init into resetting / !reestting case

[imp]

Summary

When we start the controller the first time, we're not resetting. Every
other time we start the controller, we're restting. Create the lock and
set the controller / nsid the first time through only. The 'nn' field
can't change on a reset (but the number of active namespaces might).

Sponsored by: Netflix

[imp]

Update per review, add missing change