PPC32: fix in_atomic; PREEMPT_ACTIVE set doesn't mean atomic.

include/asm-ppc/hardirq.h

@@ -82,7 +82,7 @@ typedef struct {
 #define irq_enter()		(preempt_count() += HARDIRQ_OFFSET)
 
 #if CONFIG_PREEMPT
-# define in_atomic()	(preempt_count() != kernel_locked())
+# define in_atomic()	((preempt_count() & ~PREEMPT_ACTIVE) != kernel_locked())
 # define IRQ_EXIT_OFFSET (HARDIRQ_OFFSET-1)
 #else
 # define in_atomic()	(preempt_count() != 0)