pci/intr_remapping: Allocate irq_iommu on node

make it use the node from irq_desc.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <4A95C392.5050903@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>