A diagram in whatisRCU.txt has space character before tabs.  This commit
therefore makes this diagram consistent with elsewhere in the document:
Use one leading tab, followed by spaces for any additional whitespace
required.
Signed-off-by: Tycho Andersen <tycho@tycho.ws>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
 
 
            rcu_assign_pointer()
-                                   +--------+
+                                   +--------+
            +---------------------->| reader |---------+
            |                       +--------+         |
            |                           |              |
            |                           |              | rcu_read_lock()
            |                           |              | rcu_read_unlock()
            |        rcu_dereference()  |              |
-       +---------+                      |              |
-       | updater |<---------------------+              |
-       +---------+                                     V
+           +---------+                 |              |
+           | updater |<----------------+              |
+           +---------+                                V
            |                                    +-----------+
            +----------------------------------->| reclaimer |
-                                                +-----------+
+                                                +-----------+
              Defer:
              synchronize_rcu() & call_rcu()