acpi: Support copying properties from device tree to ACPI

Some drivers in Linux support both device tree and ACPI. U-Boot itself
uses Linux device-tree bindings for its own configuration but does not use
ACPI.

It is convenient to copy these values over to the ACPI DP table for
passing to linux. Add some convenience functions to help with this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Wolfgang Wallner <wolfgang.wallner@br-automation.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/sandbox/dts/test.dts b/arch/sandbox/dts/test.dts
index 0d8ffd1..f0d8f12 100644
--- a/arch/sandbox/dts/test.dts
+++ b/arch/sandbox/dts/test.dts
@@ -111,6 +111,7 @@
 		uint-value = <(-1234)>;
 		int64-value = /bits/ 64 <0x1111222233334444>;
 		int-array = <5678 9123 4567>;
+		str-value = "test string";
 		interrupts-extended = <&irq 3 0>;
 	};