kobj: add comment and multiple inclusion protection

Signed-off-by: NRobert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

include/linux/kobj_map.h

+/*
+ * kobj_map.h
+ */
+
+#ifndef _KOBJ_MAP_H_
+#define _KOBJ_MAP_H_
+
 #include <linux/mutex.h>
 
 typedef struct kobject *kobj_probe_t(dev_t, int *, void *);
@@ -8,3 +15,5 @@ int kobj_map(struct kobj_map *, dev_t, unsigned long, struct module *,
 void kobj_unmap(struct kobj_map *, dev_t, unsigned long);
 struct kobject *kobj_lookup(struct kobj_map *, dev_t, int *);
 struct kobj_map *kobj_map_init(kobj_probe_t *, struct mutex *);
+
+#endif /* _KOBJ_MAP_H_ */