[S390] kernel: Pass correct stack for smp_call_ipl_cpu()

Currently pcpu_devices->panic_stack is passed to pcpu_delegate() in
smp_call_ipl_cpu(). This is wrong because pcpu_delegate() expects
the bottom (high address) of the stack and pcpu_devices->panic_stack
points to the top (low address). We now pass the bottom of the stack
which is pcpu_devices->panic_stack + PAGE_SIZE.
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/smp.c

@@ -335,7 +335,8 @@ void smp_call_online_cpu(void (*func)(void *), void *data)
  */
 void smp_call_ipl_cpu(void (*func)(void *), void *data)
 {
-	pcpu_delegate(&pcpu_devices[0], func, data, pcpu_devices->panic_stack);
+	pcpu_delegate(&pcpu_devices[0], func, data,
+		      pcpu_devices->panic_stack + PAGE_SIZE);
 }
 
 int smp_find_processor_id(u16 address)