dt-bindings: iio: maxim_thermocouple: document new 'compatible' strings

Now the maxim_thermocouple has new, more specific, 'compatible' strings for
better distinguish the various supported chips.

This patch updates the DT bindings documentation accordingly

Cc: Hartmut Knaack <knaack.h@gmx.de>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Patrick Havelange <patrick.havelange@essensium.com>
Cc: Matt Weber <matthew.weber@rockwellcollins.com>
Cc: Matt Ranostay <matt.ranostay@konsulko.com>
Cc: Chuhong Yuan <hslester96@gmail.com>
Cc: Daniel Gomez <dagmcr@gmail.com>
Cc: linux-iio@vger.kernel.org
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: devicetree@vger.kernel.org
Signed-off-by: Andrea Merello <andrea.merello@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/temperature/maxim_thermocouple.txt

@@ -5,7 +5,10 @@ Maxim thermocouple support
 
 Required properties:
 
-	- compatible: must be "maxim,max31855" or "maxim,max6675"
+	- compatible: must be "maxim,max6675" or one of the following:
+	   "maxim,max31855k", "maxim,max31855j", "maxim,max31855n",
+	   "maxim,max31855s", "maxim,max31855t", "maxim,max31855e",
+	   "maxim,max31855r"; the generic "max,max31855" is deprecated.
 	- reg: SPI chip select number for the device
 	- spi-max-frequency: must be 4300000
 	- spi-cpha: must be defined for max6675 to enable SPI mode 1
@@ -15,7 +18,7 @@ Required properties:
 Example:
 
 	max31855@0 {
-		compatible = "maxim,max31855";
+		compatible = "maxim,max31855k";
 		reg = <0>;
 		spi-max-frequency = <4300000>;
 	};