[PATCH] nvme: add wrapper for nvme ctrl register r/w

[Christoph Hellwig]

On Wed, Jul 12, 2017 at 01:34:14PM +0300, Sagi Grimberg wrote:
> Not sure whats special about register read/write that they
> deserve a wrapper, but its easy enough to get in before
> my patches if I'll see a review on it.

Mostly because it's a little shorter and we're only going to get
more and more of these calls.  In the end I don't feel strongly
and we can just skip the patch for now and reconsider it once
we have more register read/write calls.