pinctrl: aspeed: dt: Fix compatibles for the System Control Unit

Reference the SoC-specific compatible string in the examples as
required.
Signed-off-by: NAndrew Jeffery <andrew@aj.id.au>
Acked-by: NJoel Stanley <joel@jms.id.au>
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/pinctrl-aspeed.txt

@@ -11,9 +11,14 @@ Required properties:
 		"aspeed,ast2500-pinctrl"
 		"aspeed,g5-pinctrl"
 
-The pin controller node should be a child of a syscon node with the required
+The pin controller node should be the child of a syscon node with the required
 property:
-- compatible: "syscon", "simple-mfd"
+
+- compatible : 		Should be one of the following:
+			"aspeed,ast2400-scu", "syscon", "simple-mfd"
+			"aspeed,g4-scu", "syscon", "simple-mfd"
+			"aspeed,ast2500-scu", "syscon", "simple-mfd"
+			"aspeed,g5-scu", "syscon", "simple-mfd"
 
 Refer to the the bindings described in
 Documentation/devicetree/bindings/mfd/syscon.txt
@@ -50,7 +55,7 @@ TIMER7 TIMER8 VGABIOSROM
 Examples:
 
 syscon: scu@1e6e2000 {
-	compatible = "syscon", "simple-mfd";
+	compatible = "aspeed,ast2400-scu", "syscon", "simple-mfd";
 	reg = <0x1e6e2000 0x1a8>;
 
 	pinctrl: pinctrl {