[IA64] perfmon fix for global IRQ fix

Missed one piece of ia64 fallout from the global IRQ patch
 7d12e780

Perfmon interrupt handler needs to use get_irq_regs() too.
Acked-by: Nstephane eranian <eranian@hpl.hp.com>
Signed-off-by: NTony Luck <tony.luck@intel.com>

arch/ia64/kernel/perfmon.c

@@ -5558,12 +5558,13 @@ pfm_do_interrupt_handler(int irq, void *arg, struct pt_regs *regs)
 }
 
 static irqreturn_t
-pfm_interrupt_handler(int irq, void *arg, struct pt_regs *regs)
+pfm_interrupt_handler(int irq, void *arg)
 {
 	unsigned long start_cycles, total_cycles;
 	unsigned long min, max;
 	int this_cpu;
 	int ret;
+	struct pt_regs *regs = get_irq_regs();
 
 	this_cpu = get_cpu();
 	if (likely(!pfm_alt_intr_handler)) {