iommu/riscv: Use the generic iommu page table

iommu/riscv: Use the generic iommu page table

This is a fairly straightforward conversion of the RISC-V iommu driver to
use the generic iommu page table code.

Invalidation stays as it is now with the driver pretending to implement
simple range based invalidation even though the HW is more like ARM SMMUv3
than AMD where the HW implements a single-PTE based invalidation. Future
work to extend the generic invalidate mechanism to support more ARM-like
semantics would benefit this driver as well.

Delete the existing page table code.

Tested-by: Vincent Chen <vincent.chen@sifive.com>
Acked-by: Paul Walmsley <pjw@kernel.org> # arch/riscv
Reviewed-by: Tomasz Jeznach <tjeznach@rivosinc.com>
Tested-by: Tomasz Jeznach <tjeznach@rivosinc.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>