Stagin: lustre: Fix externs should be avoided in .c

This patch moves extern declaration from genops.c to obd_class.h,
addressing checkpatch.pl warning: externs should be avoided in .c
Signed-off-by: Haneen Mohammed <hamohammed.sa@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/include/obd_class.h

@@ -72,6 +72,7 @@ extern int lustre_get_jobid(char *jobid);
 struct lu_device_type;
 
 /* genops.c */
+extern struct list_head obd_types;
 struct obd_export *class_conn2export(struct lustre_handle *);
 int class_register_type(struct obd_ops *, struct md_ops *,
 			struct lprocfs_vars *, const char *nm,

drivers/staging/lustre/lustre/obdclass/genops.c

@@ -43,7 +43,6 @@
 #include "../include/obd_class.h"
 #include "../include/lprocfs_status.h"
 
-extern struct list_head obd_types;
 spinlock_t obd_types_lock;
 
 struct kmem_cache *obd_device_cachep;