arm: dts: icnova-a20-adb4006: Add board support

Add board support for ICnova A20 SomPi compute module on
ICnova ADB4006 development board.

Specification:
SoM
- Processor: Allwinner A20 Cortex-A7 Dual Core at 1GHz
- 512MB DDR3 RAM
- Fast Ethernet (Phy: Realtek RTL8201CP)
ADB4006
- I2C
- 2x USB 2.0
- 1x Fast Ethernet port
- 1x SATA
- 2x buttons (PWRON, Boot)
- 2x LEDS
- serial console
- HDMI
- µSD-Card slot
- Audio Line-In / Line-Out
- GPIO pinheaders

https://wiki.in-circuit.de/index.php5?title=ICnova_ADB4006
https://wiki.in-circuit.de/index.php5?title=ICnova_A20_SODIMM

devicetree upstreamed with linux 6.5

Signed-off-by: Ludwig Kormann <ludwig.kormann@ict42.de>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
diff --git a/board/sunxi/MAINTAINERS b/board/sunxi/MAINTAINERS
index 4bbe3f6..0061437 100644
--- a/board/sunxi/MAINTAINERS
+++ b/board/sunxi/MAINTAINERS
@@ -236,6 +236,11 @@
 S:	Maintained
 F:	configs/icnova-a20-swac_defconfig
 
+ICnova-A20-ADB4006 BOARD
+M:	Ludwig Kormann <ludwig.kormann@ict42.de>
+S:	Maintained
+F:	configs/icnova-a20-adb4006_defconfig
+
 ITEAD IBOX BOARD
 M:	Marcus Cooper <codekipper@gmail.com>
 S:	Maintained