of: Fix property name in of_node_get_device_type

Commit 0413bedabc ("of: Add device_type access helper functions")
added a new helper not yet used in preparation for some treewide clean
up of accesses to 'device_type' properties. Unfortunately, there's an
error and 'type' was used for the property name. Fix this.

Fixes: 0413bedabc ("of: Add device_type access helper functions")
Cc: Frank Rowand <frowand.list@gmail.com>
Signed-off-by: Rob Herring <robh@kernel.org>

include/linux/of.h

@@ -991,7 +991,7 @@ static inline struct device_node *of_find_matching_node(
 
 static inline const char *of_node_get_device_type(const struct device_node *np)
 {
-	return of_get_property(np, "type", NULL);
+	return of_get_property(np, "device_type", NULL);
 }
 
 static inline bool of_node_is_type(const struct device_node *np, const char *type)