powerpc/pmac/smp: Remove no-longer needed preempt workaround

The generic code properly re-initializes the preempt count in the
idle thread now
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/powermac/smp.c

@@ -950,13 +950,6 @@ static void pmac_cpu_die(void)
 	generic_set_cpu_dead(cpu);
 	smp_wmb();
 
-	/*
-	 * during the path that leads here preemption is disabled,
-	 * reenable it now so that when coming up preempt count is
-	 * zero correctly
-	 */
-	preempt_enable();
-
 	/*
 	 * Re-enable interrupts. The NAP code needs to enable them
 	 * anyways, do it now so we deal with the case where one already