sys: Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

rtwn: Restore RF_ENV control type after initializing RF.

Both rwlwifi in Linux and rtwn in OpenBSD restore this register,
and the existing code was saving the value and not using it.

Reported by: -Wunused-but-set-variable
Reviewed by: imp
Obtained from: OpenBSD
Differential Revision: https://reviews.freebsd.org/D34838

Add support for the Realtek RTL8192EU chipset.
Committed over the D-Link DWA-131 rev E1 on amd64 with WPA.

Reviewed by: avos