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

[Christoph Hellwig]

On Fri, Jun 30, 2017 at 01:26:24AM +0800, weiping zhang wrote:
> Simplify nvme ctrl register r/w code.
> 
> Signed-off-by: weiping zhang <zhangweiping at didichuxing.com>

This seems generally useful, especially with more consolidation
of code to the core.  Sagi - do you want to integrate this into
your consolidation series and fixup any clashes?