rcu: Remove "extern" from function declaration in include/linux/rcupdate.h

Because functions have the extern storage class specifier by default,
this keyword can be removed. It is redundant to use it explicitly.

Signed-off-by: Iulia Manda <iulia.manda21@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 00a7fd6..fdc422f 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -328,7 +328,7 @@
 extern struct lockdep_map rcu_bh_lock_map;
 extern struct lockdep_map rcu_sched_lock_map;
 extern struct lockdep_map rcu_callback_map;
-extern int debug_lockdep_rcu_enabled(void);
+int debug_lockdep_rcu_enabled(void);
 
 /**
  * rcu_read_lock_held() - might we be in RCU read-side critical section?