[POWERPC] ppc: Add missing calls to set_irq_regs

In the timer_interrupt we were not calling set_irq_regs() and if we are
profiling we will end up calling get_irq_regs().  This causes bad things to
happen.
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

arch/ppc/kernel/time.c

@@ -62,6 +62,7 @@
 #include <asm/cache.h>
 #include <asm/8xx_immap.h>
 #include <asm/machdep.h>
+#include <asm/irq_regs.h>
 
 #include <asm/time.h>
 
@@ -129,6 +130,7 @@ void wakeup_decrementer(void)
  */
 void timer_interrupt(struct pt_regs * regs)
 {
+	struct pt_regs *old_regs;
 	int next_dec;
 	unsigned long cpu = smp_processor_id();
 	unsigned jiffy_stamp = last_jiffy_stamp(cpu);
@@ -137,6 +139,7 @@ void timer_interrupt(struct pt_regs * regs)
 	if (atomic_read(&ppc_n_lost_interrupts) != 0)
 		do_IRQ(regs);
 
+	old_regs = set_irq_regs(regs);
 	irq_enter();
 
 	while ((next_dec = tb_ticks_per_jiffy - tb_delta(&jiffy_stamp)) <= 0) {
@@ -188,6 +191,7 @@ void timer_interrupt(struct pt_regs * regs)
 		ppc_md.heartbeat();
 
 	irq_exit();
+	set_irq_regs(old_regs);
 }
 
 /*