[POWERPC] ppc64: support CONFIG_DEBUG_PREEMPT

Add CONFIG_DEBUG_PREEMPT support to ppc64: it was useful for testing
get_paca() preemption.  Cheat a little, just use debug_smp_processor_id()
in the debug version of get_paca(): it contains all the right checks and
reporting, though get_paca() doesn't really use smp_processor_id().

Use local_paca for what might have been called __raw_get_paca().
Silence harmless warnings from io.h and lparcfg.c with local_paca -
it is okay for iseries_lparcfg_data to be referencing shared_proc
with preemption enabled: all cpus should show the same value for
shared_proc.

Why do other architectures need TRACE_IRQFLAGS_SUPPORT for DEBUG_PREEMPT?
I don't know, ppc64 appears to get along fine without it.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/include/asm-powerpc/smp.h b/include/asm-powerpc/smp.h
index d037f50..19102bf 100644
--- a/include/asm-powerpc/smp.h
+++ b/include/asm-powerpc/smp.h
@@ -45,7 +45,7 @@
 #endif
 
 #ifdef CONFIG_PPC64
-#define raw_smp_processor_id()	(get_paca()->paca_index)
+#define raw_smp_processor_id()	(local_paca->paca_index)
 #define hard_smp_processor_id() (get_paca()->hw_cpu_id)
 #else
 /* 32-bit */