nvme: Eliminate intel_log_temp_stats_swapbytes

We can't post a AER for this page, so there's no need to be able to swap
it to host byte order. It's not one of the standard defined pages that
can post via AER, and the vendor's public docs for this temperature page
don't suggest it's possible to get over or under event changes. Since
nvmecontrol no longer needsd the swap routine, remove it since it's
now unused.

Sponsored by: Netflix
Reviewed by: chuck
Differential Revision: https://reviews.freebsd.org/D44659