powerpc/mpic: Break cpumask abstraction earlier

mpic_set_affinity is allocating and freeing a cpumask var even though
it was breaking the cpumask abstraction when passing the mask to
mpic_physmask.  It also didn't have any check for allocatin failure.

Break the cpumask abstraction earlier and use simple bitwise and of the
bits from the mask with the bits of cpu_online_mask.
Signed-off-by: Milton Miller <miltonm@bga.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/sysdev/mpic.c

@@ -821,16 +821,12 @@ int mpic_set_affinity(struct irq_data *d, const struct cpumask *cpumask,
 
 		mpic_irq_write(src, MPIC_INFO(IRQ_DESTINATION), 1 << cpuid);
 	} else {
-		cpumask_var_t tmp;
+		u32 mask = cpumask_bits(cpumask)[0];
 
-		alloc_cpumask_var(&tmp, GFP_KERNEL);
-
-		cpumask_and(tmp, cpumask, cpu_online_mask);
+		mask &= cpumask_bits(cpu_online_mask)[0];
 
 		mpic_irq_write(src, MPIC_INFO(IRQ_DESTINATION),
-			       mpic_physmask(cpumask_bits(tmp)[0]));
-
-		free_cpumask_var(tmp);
+			       mpic_physmask(mask));
 	}
 
 	return 0;