hconf(4): Do not fetch report before writing new usage values back.

There is a report that reading of surface/button switch feature report
causes SYN1B7D touchpad malfunction. As specs does not require it to
be readable assume that report usages have default value on attach and
last written value during operation. Do not apply default usage values
on attachment and resume.
While here fix manpage typos and add avg@ to copyright header.

Reported by: Jakob Alvermark <jakob_AT_alvermark_DOT_net>
Reviewed by: avg
Differential revision: https://reviews.freebsd.org/D28196