iommu/amd: Use iommu_alloc_pages_node_sz() for the IRT

Use the actual size of the irq_table allocation, limiting to 128 due to
the HW alignment needs.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/22-v4-c8663abbb606+3f7-iommu_pages_jgg@nvidia.com


Signed-off-by: Joerg Roedel <jroedel@suse.de>