dt-bindings: arm: Add Sierra Wireless modules bindings

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>

Documentation/devicetree/bindings/arm/swir.txt

+Sierra Wireless Modules device tree bindings
+--------------------------------------------
+
+Supported Modules :
+ - WP8548 : Includes MDM9615 and PM8018 in a module
+
+Sierra Wireless modules shall have the following properties :
+  Required root node property
+   - compatible: "swir,wp8548" for the WP8548 CF3 Module
+
+Board compatible values:
+  - "swir,mangoh-green-wp8548" for the mangOH green board with the WP8548 module