powerpc: stop_this_cpu: remove the cpu from the online map.

Remove the CPU from the online map to prevent smp_call_function
from sending messages to a stopped CPU.
Signed-off-by: Valentine Barshak <vbarshak@ru.mvista.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/smp.c

@@ -218,6 +218,9 @@ void crash_send_ipi(void (*crash_ipi_callback)(struct pt_regs *))
 
 static void stop_this_cpu(void *dummy)
 {
+	/* Remove this CPU */
+	set_cpu_online(smp_processor_id(), false);
+
 	local_irq_disable();
 	while (1)
 		;