sys: Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

cxgbe(4): Retire an old check.

cxgbe(4): Add code to deal with the chip's source MAC table (aka SMT).

Submitted by: Krishnamraju Eraparaju @ Chelsio
Sponsored by: Chelsio Communications