rcutorture: Add boot-time adjustment of leaf fanout

Currently, the rcutorture scripts do not test boot-time adjustment of
leaf fanout (via the rcutree.rcu_fanout_leaf boot parameter), as was noted
during testing carried out by Iftekhar Ahmed of Oregon State University.
This commit therefore adjusts TREE04's CONFIG_RCU_FANOUT_LEAF from 4 to 3,
and also adds rcutree.rcu_fanout_leaf=4 to its boot parameters.  This
change forces RCU's boot-time geometry-change code to be exercised.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

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

@@ -14,7 +14,7 @@ CONFIG_HOTPLUG_CPU=n
 CONFIG_SUSPEND=n
 CONFIG_HIBERNATION=n
 CONFIG_RCU_FANOUT=4
-CONFIG_RCU_FANOUT_LEAF=4
+CONFIG_RCU_FANOUT_LEAF=3
 CONFIG_RCU_NOCB_CPU=n
 CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n

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

@@ -1 +1 @@
-rcutorture.torture_type=rcu_bh
+rcutorture.torture_type=rcu_bh rcutree.rcu_fanout_leaf=4