mfd: max77693: Add muic of_compatible in mfd_cell

This patch adds muic of_compatible in order to use the muic device
driver in device tree.

Signed-off-by: Maciej Purski <[e-mail]>
Reviewed-by: Chanwoo Choi <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>

Documentation/devicetree/bindings/mfd/max77693.txt

···
 Optional properties for the LED child node:
 - label : see Documentation/devicetree/bindings/leds/common.txt
 
+Optional nodes:
+- max77693-muic :
+	Node used only by extcon consumers.
+	Required properties:
+		- compatible : "maxim,max77693-muic"
+
 Example:
 #include <dt-bindings/leds/common.h>
 

drivers/mfd/max77693.c

···
 		.name = "max77693-charger",
 		.of_compatible = "maxim,max77693-charger",
 	},
-	{ .name = "max77693-muic", },
+	{
+		.name = "max77693-muic",
+		.of_compatible = "maxim,max77693-muic",
+	},
 	{
 		.name = "max77693-haptic",
 		.of_compatible = "maxim,max77693-haptic",