sunxi: Add support for Bananapi M2 Ultra

The Bananapi M2 Ultra is the first publicly available development board
featuring the R40 SoC.

This patch add barebone dtsi/dts files for the R40 and Bananapi M2 Ultra,
as well as a defconfig for it.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
index ce34e3e..198693c 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -304,6 +304,8 @@
 	sun8i-h3-orangepi-plus2e.dtb \
 	sun8i-h3-nanopi-neo.dtb \
 	sun8i-h3-nanopi-neo-air.dtb
+dtb-$(CONFIG_MACH_SUN8I_R40) += \
+	sun8i-r40-bananapi-m2-ultra.dtb
 dtb-$(CONFIG_MACH_SUN50I_H5) += \
 	sun50i-h5-orangepi-pc2.dtb
 dtb-$(CONFIG_MACH_SUN50I) += \