NVMe: Translate NVMe status to errno

This returns a more appropriate error for the "capacity exceeded"
status. In case other NVMe statuses have a better errno, this patch adds
a convience function to translate an NVMe status code to an errno for
IO commands, defaulting to the current -EIO.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>