mgb.4, muge.4: Use standard HARDWARE introduction

Release notes are generated using this text.

I used "interfaces" not "adapters" in these pages as the listed devices
are the controller ICs, not end-user projects.

Reviewed by: ziaee
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D53846

(cherry picked from commit a4aa7df767e0df49ca3294d2b578be25812364d8)