There is region left by ATF, which needs to remain in memory to provide RT
services. To prevent overwriting it by u-boot, do not provide any mapping
for this memory region, so any attempt to access it will trigger
synchronous exception.

Update sr 2021-04-12:
Don't update armada3700/cpu.c mmu table, as this has specific changes
included in mainline.
Signed-off-by: NGrzegorz Jaszczyk <jaz@semihalf.com>
Signed-off-by: NStefan Roese <sr@denx.de>