MFC r319603, r319608, r319609:

Create a hard link for sun7i-a20-cubieboard2.dtb to allow the
cubieboard2 to find the correct dtb file.

Note: r319608 and r319609 are included, but are no-op changes to
the original change, and only included to prevent these commits
from showing up on the MFC tracking page.

Approved by: re (marius)
Sponsored by: The FreeBSD Foundation