nvme: Update comment

Fix comment to note we should grab additional data from the error log
page, but don't currently (it's inclear if we should do that here
and other places in nvd that want it, or if we should let nvd / the
nda periph make the request).

Sponsored by: Netflix
Reviewed by: chuck, mav, jhb
Differential Revision: https://reviews.freebsd.org/D41315