sys: Import snapshot of Aquantia ACQ107 vendor driver

Obtained from https://github.com/Aquantia/aqtion-freebsd commit
c61d27b1d94af72c642deefa0595884481ea7377.

This is not using a vendor branch. The formerly-upstream repo is
abandoned and I do not believe it will receive updates. This initial
import serves as a snapshot of the vendor code, but from here we will
iterate on it in the tree as our own code.

Bug fixes, code cleanup, and build infrastructure will follow.

NetBSD and OpenBSD have derivatives of this driver (with additional
hardware support). We can look to changes in those drivers, and the
Linux driver, to add support here.

Reviewed by: adrian
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D53813