rcutorture: Remove SRCU-lite scenarios

This commit prepares for the removal of SRCU-Lite by removing the SRCU-L
rcutorture scenario that tests it.

Both SRCU-lite and SRCU-fast provide faster readers by dropping the
smp_mb() call from their lock and unlock primitives, but incur a pair
of added RCU grace periods during the SRCU grace period. There is a
trivial mapping from the SRCU-lite API to that of SRCU-fast, so there
should be no transition issues.

[ paulmck: Apply Christoph Hellwig feedback. ]

Signed-off-by: "Paul E. McKenney" <[e-mail]>
Signed-off-by: Neeraj Upadhyay (AMD) <[e-mail]>

tools/testing/selftests/rcutorture/configs/rcu/CFLIST

···
 TREE05
 TREE07
 TREE09
-SRCU-L
 SRCU-N
 SRCU-P
 SRCU-T

tools/testing/selftests/rcutorture/configs/rcu/SRCU-L

···
-CONFIG_RCU_TRACE=n
-CONFIG_SMP=y
-CONFIG_NR_CPUS=6
-CONFIG_HOTPLUG_CPU=y
-CONFIG_PREEMPT_NONE=y
-CONFIG_PREEMPT_VOLUNTARY=n
-CONFIG_PREEMPT=n
-#CHECK#CONFIG_RCU_EXPERT=n
-CONFIG_KPROBES=n
-CONFIG_FTRACE=n

tools/testing/selftests/rcutorture/configs/rcu/SRCU-L.boot

···
-rcutorture.torture_type=srcu
-rcutorture.reader_flavor=0x4
-rcutorture.fwd_progress=3