Create hard links to the installed dtb files for the BEAGLEBONE [1]
and WANDBOARD [2] images to fix a boot issue.

This is a direct commit to stable/10, as the change is not needed
for head and stable/11.

Approved by: re (marius)
Help from: manu [1], ian [2]
Tested by: gjb [1], ian [2]
Sponsored by: The FreeBSD Foundation