dt-bindings: arm: Add bindings for Unisoc's UMS512

Added bindings for Unisoc's ums512-1h10 board and ums512 SoC.

Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211008034533.343167-2-zhang.lyra@gmail.com

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Signed-off-by: Arnd Bergmann <arnd@arndb.de>