rcu: fix synchronize_rcu() so that kernel-doc works

Fix RCU's synchronize_rcu() so that it looks like a C function, enabling
it to be recognized as a function with kernel-doc annotation.

Warning(linux-2.6.26-git11//kernel/rcupdate.c:81): No description found for parameter 'synchronize_rcu'
Warning(linux-2.6.26-git11//kernel/rcupdate.c:81): No description found for parameter 'call_rcu'

[[e-mail]: fix comment]
Signed-off-by: Randy Dunlap <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Ingo Molnar <[e-mail]>

kernel/rcupdate.c

···
  * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
  * and may be nested.
  */
+void synchronize_rcu(void);	/* Makes kernel-doc tools happy */
 synchronize_rcu_xxx(synchronize_rcu, call_rcu)
 EXPORT_SYMBOL_GPL(synchronize_rcu);