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

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

Add support for the Allwinner DMA controller. This will be used by the at
least the audio codec driver currently in review.

Submitted by: Jared McNeill <jmcneill@invisible.ca>
Differential Revision: https://reviews.freebsd.org/D5050