rcu: Remove "extern" from function declarations in include/linux/*rcu*.h

Function prototypes don't need to have the "extern" keyword since this
is the default behavior. Its explicit use is redundant.  This commit
therefore removes them.

Signed-off-by: Teodora Baluta <teobaluta@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index 45a0a9e..dbaf990 100644
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -55,8 +55,8 @@
 	next->prev = new;
 }
 #else
-extern void __list_add_rcu(struct list_head *new,
-		struct list_head *prev, struct list_head *next);
+void __list_add_rcu(struct list_head *new,
+		    struct list_head *prev, struct list_head *next);
 #endif
 
 /**