dt-bindings: hwmon: add compatible for max1619

Add new device tree bindings document for max1619 device
including a new compatible string.
Signed-off-by: Alan Tull <atull@kernel.org>
Cc: Jean Delvare <jdelvare@suse.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/devicetree/bindings/hwmon/max1619.txt

+Bindings for MAX1619 Temperature Sensor
+
+Required properties:
+- compatible : "maxim,max1619"
+- reg        : I2C address, one of 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b, 0x4c, or
+               0x4d, 0x4e
+
+Example:
+	temp@4c {
+		compatible = "maxim,max1619";
+		reg = <0x4c>;
+	};