arm: mvebu: Espressobin: Change default loadaddr

Current loadaddr is not writable on Espressobin and 'loadb' command cause
rebooting board. Marvell's U-Boot already set default loadaddr to value
0x06000000 [1] and after this change 'loadb' is working fine.

[1] - https://github.com/MarvellEmbeddedProcessors/u-boot-marvell/commit/0a5b159806baa0746b6449920e450498bc269ba7



Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-by: Andre Heider <a.heider@gmail.com>