[PATCH 4/7] nvme: implement multipath access to nvme subsystems

[Christoph Hellwig]

> If we've CMIC capabilities, we'll use the subsys->instance; if we don't
> have CMIC, we use the ctrl->instance. 
> 
> Since the two instances are independent of each other, they can create
> duplicate names.
> 
> To fix, I think we'll need to always use the subsys instance for
> consistency if CONFIG_NVME_MULTIPATH=y.

Yes, we should.  But once we do that we should just always use
subsys->instance, as it will always be the same as ctrl->instance
for CONFIG_NVME_MULTIPATH=n.