dt-bindings: reset: Add bindings for the Meson-AXG SoC Reset Controller

Add DT bindings for the Meson-AXG SoC Reset Controller include file,
and also slightly update documentation.

Signed-off-by: Yixun Lan <yixun.lan@amlogic.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

Documentation/devicetree/bindings/reset/amlogic,meson-reset.txt

@@ -5,7 +5,8 @@ Please also refer to reset.txt in this directory for common reset
 controller binding usage.
 
 Required properties:
-- compatible: Should be "amlogic,meson8b-reset" or "amlogic,meson-gxbb-reset"
+- compatible: Should be "amlogic,meson8b-reset", "amlogic,meson-gxbb-reset" or
+	"amlogic,meson-axg-reset".
 - reg: should contain the register address base
 - #reset-cells: 1, see below