rcutorture: Make TREE04 use CONFIG_RCU_DYNTICKS_TORTURE

We now have an RCU_EXPERT config for testing small-sized RCU dynticks
counter:  CONFIG_RCU_DYNTICKS_TORTURE.

Modify scenario TREE04 to exercise to use this config in order to test a
ridiculously small counter (2 bits).

Link: http://lore.kernel.org/r/4c2cb573-168f-4806-b1d9-164e8276e66a@paulmck-laptop
Suggested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>

Author: valschneider

tools/testing/selftests/rcutorture/configs/rcu/TREE04

@@ -16,3 +16,4 @@ CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
 CONFIG_RCU_EXPERT=y
 CONFIG_RCU_EQS_DEBUG=y
 CONFIG_RCU_LAZY=y
+CONFIG_RCU_DYNTICKS_TORTURE=y