iwlwifi: update man pages

Update man pages given auto-loading is now enabled by default and
no user configuration is needed to load the driver.
Also note that the iwlwifi driver will appear the first time in 13.1-R.

Sponsored by: The FreeBSD Foundation
Relnotes: yes

(cherry picked from commit abf6e1a49e944f9fb635a6aed55f01af832da06c)