mfd: max77686: Use a generic name for the PMIC node in the example

The ePAPR standard says that: "the name of a node should be somewhat
generic, reflecting the function of the device and not its precise
programming model."

So, change the max77686 binding document example to use a generic
node name instead of using the chip's name.
Suggested-by: NSergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: NJavier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: NLee Jones <lee.jones@linaro.org>

Documentation/devicetree/bindings/mfd/max77686.txt

@@ -48,7 +48,7 @@ to get matched with their hardware counterparts as follow:
 
 Example:
 
-	max77686@09 {
+	max77686: pmic@09 {
 		compatible = "maxim,max77686";
 		interrupt-parent = <&wakeup_eint>;
 		interrupts = <26 0>;