mips: Validate online cpus in irq_set_affinity() callbacks

The [user space] interface does not filter out offline cpus. It merily
guarantees that the mask contains at least one online cpu.

So the selector in the irq chip implementation needs to make sure to
pick only an online cpu because otherwise:

     Offline Core 1
     Set affinity to 0xe (is valid due to online mask 0xd)
     cpumask_first will pick core 1, which is offline
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Link: http://lkml.kernel.org/r/20140304203100.744800502@linutronix.deSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/mips/sibyte/bcm1480/irq.c

@@ -95,7 +95,7 @@ static int bcm1480_set_affinity(struct irq_data *d, const struct cpumask *mask,
 	u64 cur_ints;
 	unsigned long flags;
 
-	i = cpumask_first(mask);
+	i = cpumask_first_and(mask, cpu_online_mask);
 
 	/* Convert logical CPU to physical CPU */
 	cpu = cpu_logical_map(i);

arch/mips/sibyte/sb1250/irq.c

@@ -88,7 +88,7 @@ static int sb1250_set_affinity(struct irq_data *d, const struct cpumask *mask,
 	u64 cur_ints;
 	unsigned long flags;
 
-	i = cpumask_first(mask);
+	i = cpumask_first_and(mask, cpu_online_mask);
 
 	/* Convert logical CPU to physical CPU */
 	cpu = cpu_logical_map(i);