arm: vf610twr: improve memory layout

Currently, the device tree relocation is disabled, likely to
keep some DDR3 RAM at the end for Cortex-M4 firmwares. This
can be archived using bootm_size, which limits the image
processing range of the boot commands.

Move the device tree standard load address to a higher address
which aligns better with what we are doing on other boards.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Acked-by: Otavio Salvador <otavio@ossystems.com.br>