dt-bindings: pinctrl: rt2880: properly redo bindings

When this bindings where applied there weren't already
reviewed and some old hacks was being used to properly
pass the schemas checks. This commits fix them up:
 - Instead of using 'if-then' clause use '-pins$'.
 - 'groups' and 'function' are included inside a new
   '^(.*-)?pinmux$' node.
 - compatible string is not an 'enum' but a 'const'.
 - 'pinctrl-0' and 'pinctrl-names' removed since they are
    used in consumer nodes.
Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20201213161721.6514-2-sergio.paracuellos@gmail.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/ralink,rt2880-pinmux.yaml

@@ -15,29 +15,17 @@ description:
 
 properties:
   compatible:
-    enum:
-      - ralink,rt2880-pinmux
-
-  pinctrl-0:
-    description:
-      A phandle to the node containing the subnodes containing default
-      configurations. This is for pinctrl hogs.
-
-  pinctrl-names:
-    description:
-      A pinctrl state named "default" can be defined.
-    const: default
-
-required:
-  - compatible
+    const: ralink,rt2880-pinmux
 
 patternProperties:
-  '[a-z0-9_-]+':
-    if:
+  '-pins$':
+    type: object
+    patternProperties:
+      '^(.*-)?pinmux$':
         type: object
         description: node for pinctrl.
-      $ref: "pinmux-node.yaml"
-    then:
+        $ref: pinmux-node.yaml#
+
         properties:
           groups:
             description: Name of the pin group to use for the functions.
@@ -48,6 +36,17 @@ patternProperties:
             enum: [gpio, i2c, spi, uart1, uart2, uart3, rgmii1, rgmii2,
                    mdio, nand1, nand2, sdhci]
 
+        required:
+          - groups
+          - function
+
+        additionalProperties: false
+
+    additionalProperties: false
+
+required:
+  - compatible
+
 additionalProperties: false
 
 examples:
@@ -55,14 +54,9 @@ examples:
   - |
     pinctrl {
       compatible = "ralink,rt2880-pinmux";
-      pinctrl-names = "default";
-      pinctrl-0 = <&state_default>;
-
-      state_default: pinctrl0 {
-      };
 
-      i2c_pins: i2c0 {
-        i2c0 {
+      i2c_pins: i2c0-pins {
+        pinmux {
           groups = "i2c";
           function = "i2c";
         };