Set device_tree_address to an empty value for Pi 5, overriding the
inherited 0x4000 address and allowing firmware to place the DTB.
Keep DTB selection automatic for the D0 overlay. Preserve other models'
settings and bump PORTREVISION.

Companion src driver and release changes are required for Pi 5 support.

Tested on one Raspberry Pi 5 Model B 8GB (BCM2712 D0, revision code
0xd04171), using an image with the companion src patches.
A fixed DTB address of 0x4000 stopped boot after the BL31 banner.
An empty Pi 5 address override let firmware choose 0x2efec500 and load
the D0 overlay. FreeBSD booted successfully; interactive UART login and
console output on an HDMI monitor were confirmed.

Hardware validation was limited to this board.