dt-bindings: interrupt-controller: New binding for Meson-G12A SoC

Update the dt-binding document to support new compatible string for the
GPIO interrupt controller which found in Amlogic's Meson-G12A SoC.

Signed-off-by: Xingyu Chen <xingyu.chen@amlogic.com>
Signed-off-by: Jianxin Pan <jianxin.pan@amlogic.com>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Documentation/devicetree/bindings/interrupt-controller/amlogic,meson-gpio-intc.txt

@@ -15,6 +15,7 @@ Required properties:
     "amlogic,meson-gxbb-gpio-intc" for GXBB SoCs (S905) or
     "amlogic,meson-gxl-gpio-intc" for GXL SoCs (S905X, S912)
     "amlogic,meson-axg-gpio-intc" for AXG SoCs (A113D, A113X)
+    "amlogic,meson-g12a-gpio-intc" for G12A SoCs (S905D2, S905X2, S905Y2)
 - reg : Specifies base physical address and size of the registers.
 - interrupt-controller : Identifies the node as an interrupt controller.
 - #interrupt-cells : Specifies the number of cells needed to encode an