dt-bindings: display: amlogic, meson-vpu: Add G12A compatible and ports

The Amlogic G12A VPU is very similar to the Amlogic GXM VPU but with :
- an enhanced plane blender, with up to 3 OSD planes
- support for AFBC 1.2 decoder (for Bifrost GPU)
- support display mode up to 4k60@75Hz
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190313141030.5958-2-narmstrong@baylibre.com

Documentation/devicetree/bindings/display/amlogic,meson-vpu.txt

@@ -57,6 +57,7 @@ Required properties:
 	- GXL (S905X, S905D) : "amlogic,meson-gxl-vpu"
 	- GXM (S912) : "amlogic,meson-gxm-vpu"
 	followed by the common "amlogic,meson-gx-vpu"
+	- G12A (S905X2, S905Y2, S905D2) : "amlogic,meson-g12a-vpu"
 - reg: base address and size of he following memory-mapped regions :
 	- vpu
 	- hhi
@@ -83,6 +84,9 @@ corresponding to each VPU output.
  S905X (GXL)	CVBS VDAC	HDMI-TX
  S905D (GXL)	CVBS VDAC	HDMI-TX
  S912 (GXM)	CVBS VDAC	HDMI-TX
+ S905X2 (G12A)	CVBS VDAC	HDMI-TX
+ S905Y2 (G12A)	CVBS VDAC	HDMI-TX
+ S905D2 (G12A)	CVBS VDAC	HDMI-TX
 
 Example: