nvmecontrol: Fix to128 for big endian targets

The source is always 128-bits in little endian format. For big endian
hosts, we have to convert, or we print bogus numbers.

Sponsored by: Netflix
Reviewed by: chuck
Differential Revision: https://reviews.freebsd.org/D44651

(cherry picked from commit 1c4b7effa7f9df64bf72c6291b4719cffb2ffe22)