In irq_2_iommu_alloc() and set_irte_irq(), irq_to_desc or
irq_2_iommu pointers may not be allocated. So use the routines
which will allocate them if they are not already allocated.
Signed-off-by: NSuresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>