hwmon: (lm70) add device tree support

Allow the lm70 to be probed from a device tree.

Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/devicetree/bindings/hwmon/lm70.txt

@@ -0,0 +1,21 @@
+* LM70/TMP121/LM71/LM74 thermometer.
+
+Required properties:
+- compatible: one of
+		"ti,lm70"
+		"ti,tmp121"
+		"ti,lm71"
+		"ti,lm74"
+
+See Documentation/devicetree/bindings/spi/spi-bus.txt for more required and
+optional properties.
+
+Example:
+
+spi_master {
+	temperature-sensor@0 {
+		compatible = "ti,lm70";
+		reg = <0>;
+		spi-max-frequency = <1000000>;
+	};
+};