refscale: Add CONFIG_PREEMPT_DYNAMIC=n to NOPREEMPT scenario

It is no longer possible to build a kernel with a preemption-disabled
RCU without use of CONFIG_PREEMPT_DYNAMIC=n.  This commit therefore
adds CONFIG_PREEMPT_DYNAMIC=n to the refscale torture type's NOPREEMPT
scenario file.

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