[RFC][PATCH 1/1]nand/denali: Add runtime pm support for denali controller driver

[Dong, Chuanxiao]

> if you take the refcount every time you get a command, and drop a count
> each time a command completes.... this is all not too important.. it'll
> just work
If I take the refcount every time I got a command and drop a count each time a command completes, the controller device will be resumed every time when it gets a command and suspended after it finishes a command. For a 4k page NAND, processing just 1M data will cause device resume/suspend 256 times....This will influence the performance....Although denali controller cannot be really resumed/suspend, to these devices who can resume/suspend, I think it is not a good way.
Right now there are 6 patches for denali MTD driver pending. After these 6 patches are accepted and Denali MTD driver can be used on MRST platform, I will resubmit a runtime pm patch. Arjan, do you agree?