riscv: dts: add OpenPiton RISC-V board dts support

Previous device tree for OpenPiton emits a warning during compilation.
This commit fixes the previous warning adds dts to the OpenPiton RISC-V
board and added the device tree to MAINTAINER file.

Signed-off-by: Tianrui Wei <tianrui-wei@outlook.com>
Reported-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
diff --git a/arch/riscv/dts/openpiton-riscv64.dts b/arch/riscv/dts/openpiton-riscv64.dts
index 45951e1..abc6016 100644
--- a/arch/riscv/dts/openpiton-riscv64.dts
+++ b/arch/riscv/dts/openpiton-riscv64.dts
@@ -80,8 +80,8 @@
 	};
 
 	soc {
-		#address-cells = <1>;
-		#size-cells = <1>;
+		#address-cells = <2>;
+		#size-cells = <2>;
 		compatible = "openpiton,chipset", "simple-bus";
 		ranges;