dt-bindings: simplefb-sunxi: add pipelines for DE2

As we're going to add simplefb support for Allwinner SoCs with DE2, add
suitable pipeline strings in the device tree binding.
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>

Documentation/devicetree/bindings/display/simple-framebuffer-sunxi.txt

@@ -15,6 +15,10 @@ Required properties:
   "de_be1-lcd1"
   "de_be0-lcd0-hdmi"
   "de_be1-lcd1-hdmi"
+  "mixer0-lcd0"
+  "mixer0-lcd0-hdmi"
+  "mixer1-lcd1-hdmi"
+  "mixer1-lcd1-tve"
 
 Example: