[IA64] Move local_softirq_pending() definition

Ugly #include dependencies. We need to have local_softirq_pending()
defined before it gets used in <linux/interrupt.h>. But <asm/hardirq.h>
provides the definition *after* this #include chain:
  <linux/irq.h>
    <asm/irq.h>
      <asm/hw_irq.h>
        <linux/interrupt.h>

Signed-off-by: Tony Luck <tony.luck@intel.com>