misc cleanups for nvme-pci

[Christoph Hellwig <hch@lst.de>]

Hi all,

this has misc cleanups for the nvme-pci I/O code.  Most of this was done
as part of the new DMA API work.  Which then clashed with the per-node
dmapools, so I'll try to get it out now instead of having to do another
rebase.  As part of that this also includes minor tidyups for the new code
from the per-node dmapools.

Diffstat:
 pci.c |  196 ++++++++++++++++++++++++++++++++----------------------------------
 1 file changed, 97 insertions(+), 99 deletions(-)