mfd: max14577: Add of_compatible to extcon mfd_cell

Add of_compatible ("maxim,max14577-muic") to the mfd_cell for extcon
driver. If entry with such compatible is present in the DTS, the extcon
driver will have of_node set.

This may be useful for extcon consumers and it is documented in
bindings documentation.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/max14577.c

@@ -25,7 +25,10 @@
 #include <linux/mfd/max14577-private.h>
 
 static struct mfd_cell max14577_devs[] = {
-	{ .name = "max14577-muic", },
+	{
+		.name = "max14577-muic",
+		.of_compatible = "maxim,max14577-muic",
+	},
 	{
 		.name = "max14577-regulator",
 		.of_compatible = "maxim,max14577-regulator",