rcutorture: Test RCU-sched primitives in TREE_PREEMPT_RCU kernels

This commit ensures that RCU-sched primitives are tested in
TREE_PREEMPT_RCU kernels, a combination that was previously omitted.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

tools/testing/selftests/rcutorture/configs/rcu/TREE08.boot

+rcutorture.torture_type=sched