cam: Add CAM_NVME_STATUS_ERROR error code

Add CAM_NVME_STATUS_ERROR error code. Flag all NVME commands that
completed with an error status as CAM_NVME_STATUS_ERROR (a new value)
instaead of CAM_REQ_CMP_ERR. This indicates to the upper layers of CAM
that the 'cpl' field for nvmeio CCBs is valid and can be examined for
error recovery, if desired.

No functional change. nda will still see these as errors, call
ndaerror() to get the error recovery action, etc. cam_periph_error will
select the same case as before (even w/o the change, though the change
makes it explicit).

Sponsored by: Netflix
Reviewed by: chuck, mav, jhb
Differential Revision: https://reviews.freebsd.org/D41085