iommu/riscv: Update to use iommu_alloc_pages_node_lg2()

One part of RISCV already has a computed size, however the queue
allocation must be aligned to 4k. The other objects are 4k by spec.

Reviewed-by: Tomasz Jeznach <tjeznach@rivosinc.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/18-v4-c8663abbb606+3f7-iommu_pages_jgg@nvidia.com


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