fix atomic limits check v2

[Christoph Hellwig]

Hi all,

this series tries to fix the atomics limit check to limit it to
the per-controller values and to the controller probing.

I think this should solve the root cause of the report from Yi Zhang,
but needs new verification.

Changes since v1:
 - initialize subsys->awupf in nvme_init_subsystem to make sure that only
   happens once per controller

Diffstat:
 core.c |   83 +++++++++++++++++++++++++++++------------------------------------
 nvme.h |    3 --
 2 files changed, 39 insertions(+), 47 deletions(-)