iommu, x86: Implement irq_set_vcpu_affinity for intel_ir_chip

iommu, x86: Implement irq_set_vcpu_affinity for intel_ir_chip

Interrupt chip callback to set the VCPU affinity for posted interrupts.

[ tglx: Use the helper function to copy from the remap irte instead of
        open coding it. Massage the comment as well ]

Signed-off-by: Feng Wu <feng.wu@intel.com>
Reviewed-by: Jiang Liu <jiang.liu@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: David Woodhouse <David.Woodhouse@intel.com>
Cc: iommu@lists.linux-foundation.org
Cc: joro@8bytes.org
Cc: dwmw2@infradead.org
Link: http://lkml.kernel.org/r/1433827237-3382-5-git-send-email-feng.wu@intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>