sunxi: defconfig: Add X96 Mate TV box

The X96 Mate TV box is a TV box with the Allwinner H616 SoC. It is
available with up to 4GB of DRAM and 64GB eMMC.
The DRAM chips require a different configuration when compared to the
OrangePi Zero2, we must not use read/write training and write leveling.

Add a defconfig for the box, so that we can easily build U-Boot for it.
We synced the .dts file already from the kernel tree.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
diff --git a/board/sunxi/MAINTAINERS b/board/sunxi/MAINTAINERS
index 5a0b598..80e3f4b 100644
--- a/board/sunxi/MAINTAINERS
+++ b/board/sunxi/MAINTAINERS
@@ -535,6 +535,11 @@
 S:	Maintained
 F:	configs/Wexler_TAB7200_defconfig
 
+X96 MATE TV BOX
+M:	Andre Przywara <andre.przywara@arm.com>
+S:	Maintained
+F:	configs/x96_mate_defconfig
+
 YONES TOPTECH BD1078 BOARD
 M:	Paul Kocialkowski <contact@paulk.fr>
 S:	Maintained