ARM: dts: artpec: disable Accelerator Coherency Port

Accesses via 0x80000000 go through the ACP instead of using the DDR
directly.

Unfortunately the ACP has proven to be the cause of complete system
hangs. Disabling the ACP makes these problems go away.

Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>