scftorture: Update due to x86 not supporting none/voluntary preemption

As of v7.0-rc1, architectures that support preemption, including x86 and
arm64, no longer support CONFIG_PREEMPT_NONE or CONFIG_PREEMPT_VOLUNTARY.
Attempting to build kernels with these two Kconfig options results in
.config errors.  This commit therefore switches such scftorture scenarios
to CONFIG_PREEMPT_LAZY.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>