arm64: dts: add device tree for ARM SMM-A53x2 on LogicTile Express 20MG

arm64: dts: add device tree for ARM SMM-A53x2 on LogicTile Express 20MG

Add a DTS file for the MP2 Cortex-A53 Soft Macrocell Model implemented
on a LogicTile Express 20MG (V2F-1XV7) daughterboard. This is based on
the version that's currently available from the ARM DTS repository [1].

[1] git://linux-arm.org/arm-dts.git

Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
Acked-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Kevin Hilman <khilman@linaro.org>