dt-bindings: gpio: aspeed,ast2400-gpio: Convert to DT schema

Squash warnings such as:

```
arch/arm/boot/dts/aspeed/aspeed-bmc-facebook-galaxy100.dtb: /ahb/apb@1e600000/gpio@1e780000: failed to match any schema with compatible: ['aspeed,ast2400-gpio']
```

Signed-off-by: Andrew Jeffery <andrew@codeconstruct.com.au>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

Documentation/devicetree/bindings/gpio/aspeed,ast2400-gpio.yaml

@@ -0,0 +1,148 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/gpio/aspeed,ast2400-gpio.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Aspeed GPIO controller
+
+maintainers:
+  - Andrew Jeffery <andrew@codeconstruct.com.au>
+
+properties:
+  compatible:
+    enum:
+      - aspeed,ast2400-gpio
+      - aspeed,ast2500-gpio
+      - aspeed,ast2600-gpio
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+    description: The clock to use for debounce timings
+
+  gpio-controller: true
+  gpio-line-names:
+    minItems: 36
+    maxItems: 232
+
+  gpio-ranges: true
+
+  "#gpio-cells":
+    const: 2
+
+  interrupts:
+    maxItems: 1
+
+  interrupt-controller: true
+
+  "#interrupt-cells":
+    const: 2
+
+  ngpios:
+    minimum: 36
+    maximum: 232
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - interrupt-controller
+  - "#interrupt-cells"
+  - gpio-controller
+  - "#gpio-cells"
+
+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: aspeed,ast2400-gpio
+    then:
+      properties:
+        gpio-line-names:
+          minItems: 220
+          maxItems: 220
+        ngpios:
+          const: 220
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: aspeed,ast2500-gpio
+    then:
+      properties:
+        gpio-line-names:
+          minItems: 232
+          maxItems: 232
+        ngpios:
+          const: 232
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: aspeed,ast2600-gpio
+    then:
+      properties:
+        gpio-line-names:
+          minItems: 36
+          maxItems: 208
+        ngpios:
+          enum: [ 36, 208 ]
+      required:
+        - ngpios
+
+additionalProperties: false
+
+examples:
+  - |
+    gpio@1e780000 {
+        compatible = "aspeed,ast2400-gpio";
+        reg = <0x1e780000 0x1000>;
+        interrupts = <20>;
+        interrupt-controller;
+        #interrupt-cells = <2>;
+        gpio-controller;
+        #gpio-cells = <2>;
+    };
+  - |
+    gpio: gpio@1e780000 {
+        compatible = "aspeed,ast2500-gpio";
+        reg = <0x1e780000 0x200>;
+        interrupts = <20>;
+        interrupt-controller;
+        #interrupt-cells = <2>;
+        gpio-controller;
+        #gpio-cells = <2>;
+        gpio-ranges = <&pinctrl 0 0 232>;
+    };
+  - |
+    #include <dt-bindings/clock/ast2600-clock.h>
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+    gpio0: gpio@1e780000 {
+        compatible = "aspeed,ast2600-gpio";
+        reg = <0x1e780000 0x400>;
+        clocks = <&syscon ASPEED_CLK_APB2>;
+        interrupts = <GIC_SPI 40 IRQ_TYPE_LEVEL_HIGH>;
+        interrupt-controller;
+        #interrupt-cells = <2>;
+        #gpio-cells = <2>;
+        gpio-controller;
+        gpio-ranges = <&pinctrl 0 0 208>;
+        ngpios = <208>;
+    };
+    gpio1: gpio@1e780800 {
+        compatible = "aspeed,ast2600-gpio";
+        reg = <0x1e780800 0x800>;
+        clocks = <&syscon ASPEED_CLK_APB1>;
+        interrupts = <GIC_SPI 11 IRQ_TYPE_LEVEL_HIGH>;
+        interrupt-controller;
+        #interrupt-cells = <2>;
+        gpio-controller;
+        #gpio-cells = <2>;
+        gpio-ranges = <&pinctrl 0 208 36>;
+        ngpios = <36>;
+    };