rcutorture: Upgrade two-CPU scenarios to four CPUs

There is no way to place the vCPUs in a two-CPU rcutorture scenario to
get variable memory latency.  This commit therefore upgrades the current
two-CPU rcutorture scenarios to four CPUs.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/testing/selftests/rcutorture/configs/rcu/RUDE01

 CONFIG_SMP=y
-CONFIG_NR_CPUS=2
+CONFIG_NR_CPUS=4
 CONFIG_HOTPLUG_CPU=y
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n

tools/testing/selftests/rcutorture/configs/rcu/TASKS01

 CONFIG_SMP=y
-CONFIG_NR_CPUS=2
+CONFIG_NR_CPUS=4
 CONFIG_HOTPLUG_CPU=y
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n

tools/testing/selftests/rcutorture/configs/rcu/TASKS03

 CONFIG_SMP=y
-CONFIG_NR_CPUS=2
+CONFIG_NR_CPUS=4
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y