Comment 4 for bug 1578745

Damn, you're right. I knew that was needed in certain situations with the new firmware (and have it being written in my MP for raspi3 support in livecd-rootfs), but for some reason thought xenial u-boot + new firmware + raspi2 didn't need it.

I'll write a configure hook for detecting the upgrade and modifying config.txt, and get back to you.

FYI, this seems to be the traditional location for the DTB (and where it was placed originally):

device_tree_address=0x100
device_tree_end=0x8000

0x100 begin is the same, but end is now 0x8000 (before the kernel area) as the xenial kernel DTB is approaching the size of (0x4000-0x100).