nvmecontrol: Move self test status page printing to little endian orderinng

Also, add printing vnedor_specific field, which doesn't have a valid
bit, so is always valid.

Sponsored by: Netflix
Reviewed by: chuck
Differential Revision: https://reviews.freebsd.org/D44654

(cherry picked from commit 98f841efd8ce387d9cd060174b9dcc9ff9850648)