hwmon: (max197) add include guard

Add include guard to include/linux/platform_data/max197.h to prevent
multiple inclusion.

Signed-off-by: Vivien Didelot <[e-mail]>
Signed-off-by: Guenter Roeck <[e-mail]>

include/linux/platform_data/max197.h

···
  * For further information, see the Documentation/hwmon/max197 file.
  */
 
+#ifndef _PDATA_MAX197_H
+#define _PDATA_MAX197_H
+
 /**
  * struct max197_platform_data - MAX197 connectivity info
  * @convert:	Function used to start a conversion with control byte ctrl.
···
 struct max197_platform_data {
 	int (*convert)(u8 ctrl);
 };
+
+#endif /* _PDATA_MAX197_H */