powerpc: Silence xics_migrate_irqs_away() during cpu offline

All IRQs are migrated away from a CPU that is being offlined so the
following messages suggest a problem when the system is behaving as
designed:

IRQ 262 affinity broken off cpu 1
IRQ 17 affinity broken off cpu 0
IRQ 18 affinity broken off cpu 0
IRQ 19 affinity broken off cpu 0
IRQ 256 affinity broken off cpu 0
IRQ 261 affinity broken off cpu 0
IRQ 262 affinity broken off cpu 0

Don't print these messages when the CPU is not online.
Signed-off-by: Darren Hart <dvhltc@us.ibm.com>
Acked-by: Will Schmidt <will_schmidt@vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Nathan Fontenot <nfont@austin.ibm.com>
Cc: Robert Jennings <rcj@linux.vnet.ibm.com>
Cc: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/pseries/xics.c

@@ -928,6 +928,8 @@ void xics_migrate_irqs_away(void)
 		if (xics_status[0] != hw_cpu)
 			goto unlock;
 
+		/* This is expected during cpu offline. */
+		if (cpu_online(cpu))
 			printk(KERN_WARNING "IRQ %u affinity broken off cpu %u\n",
 			       virq, cpu);