ARM: dts: introduce MPS2 AN399/AN400

Application Notes 399 and 400 shares the same memory map and
features. Both are shipped with Cortex-M7 and have the same  peripheral
as AN385/AN386, but with different location of PSRAM and Ethernet
controller.

Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>