dt-bindings: interrupt-controller: New binding for Meson-A1 SoCs

Update dt-binding document for GPIO interrupt controller of Meson-A1 SoCs
Signed-off-by: Qianggui Song <qianggui.song@amlogic.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20191216123645.10099-2-qianggui.song@amlogic.com

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

@@ -17,6 +17,7 @@ Required properties:
     "amlogic,meson-axg-gpio-intc" for AXG SoCs (A113D, A113X)
     "amlogic,meson-g12a-gpio-intc" for G12A SoCs (S905D2, S905X2, S905Y2)
     "amlogic,meson-sm1-gpio-intc" for SM1 SoCs (S905D3, S905X3, S905Y3)
+    "amlogic,meson-a1-gpio-intc" for A1 SoCs (A113L)
 - 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