arm: sunxi: add support for V3s SoC

Allwinner V3s is a low-end single-core Cortex-A7 SoC, with 64MB
integrated DRAM, and several peripherals.
Signed-off-by: NIcenowy Zheng <icenowy@aosc.xyz>
Signed-off-by: NMaxime Ripard <maxime.ripard@free-electrons.com>

Documentation/arm/sunxi/README

@@ -71,6 +71,10 @@ SunXi family
         + Datasheet
           http://dl.linux-sunxi.org/H3/Allwinner_H3_Datasheet_V1.0.pdf
 
+      - Allwinner V3s (sun8i)
+        + Datasheet
+          http://linux-sunxi.org/File:Allwinner_V3s_Datasheet_V1.0.pdf
+
     * Quad ARM Cortex-A15, Quad ARM Cortex-A7 based SoCs
       - Allwinner A80
         + Datasheet

arch/arm/mach-sunxi/sunxi.c

@@ -65,6 +65,7 @@ static const char * const sun8i_board_dt_compat[] = {
 	"allwinner,sun8i-a83t",
 	"allwinner,sun8i-h2-plus",
 	"allwinner,sun8i-h3",
+	"allwinner,sun8i-v3s",
 	NULL,
 };