Section 3.1 gives the comment for the offset of controller registers
in the specification 1.2a.

Some are mis-copied in the header file nvme.h. Correct them.
Signed-off-by: NWang Sheng-Hui <shhuiw@foxmail.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NSagi Grimberg <sagi@grimberg.me>
Signed-off-by: NJens Axboe <axboe@fb.com>