15.1/relnotes: LinuxKPI based wirleess drivers
Adjust the carefully prepared list of changes for the 15.1 release:
- reduce the list of driver updates to the ones we actually ship. Mediatek was in a different category anyway.
- adjust some descriptions and add notes to Realtek drivers that there are known issues.
Sponsored by: The FreeBSD Foundation
Reviewed by: vladlen
Differential Revision: https://reviews.freebsd.org/D57243