MAINTAINERS: Add Device Tree binding doc for max77686 regulator

The Device Tree binding documentation for the Maxim max77686 regulators
has been moved from the Multi-Function Device DT binding section to its
own Documentation/devicetree/bindings/regulator/max77686.txt file.

Use a wilcard so both the mfd and regulator DT bindings are resolved.
Signed-off-by: NJavier Martinez Canillas <javier@osg.samsung.com>
Reviewed-by: NKrzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: NLee Jones <lee.jones@linaro.org>

MAINTAINERS

@@ -6572,7 +6572,7 @@ F:	drivers/extcon/extcon-max77693.c
 F:	drivers/rtc/rtc-max77686.c
 F:	drivers/clk/clk-max77686.c
 F:	Documentation/devicetree/bindings/mfd/max14577.txt
-F:	Documentation/devicetree/bindings/mfd/max77686.txt
+F:	Documentation/devicetree/bindings/*/max77686.txt
 F:	Documentation/devicetree/bindings/mfd/max77693.txt
 F:	Documentation/devicetree/bindings/clock/maxim,max77686.txt
 F:	include/linux/mfd/max14577*.h