doc: Fix various RCU docbook comment-header problems

Because many of RCU's files have not been included into docbook, a
number of errors have accumulated.  This commit fixes them.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index b1fd8bf..2bea1d5 100644
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -276,7 +276,7 @@ static inline void list_splice_tail_init_rcu(struct list_head *list,
 #define list_entry_rcu(ptr, type, member) \
 	container_of(lockless_dereference(ptr), type, member)
 
-/**
+/*
  * Where are list_empty_rcu() and list_first_entry_rcu()?
  *
  * Implementing those functions following their counterparts list_empty() and