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spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

Add driver for Altera SoftDMA® device.

SoftDMA is a software implementation of DMA engine built using Altera
FIFO component.

Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D9620