vfio: selftests: Stop passing device for IOMMU operations

vfio: selftests: Stop passing device for IOMMU operations

Drop the struct vfio_pci_device wrappers for IOMMU map/unmap functions
and require tests to directly call iommu_map(), iommu_unmap(), etc. This
results in more concise code, and also makes it clear the map operations
are happening on a struct iommu, not necessarily on a specific device,
especially when multi-device tests are introduced.

Do the same for iova_allocator_init() as that function only needs the
struct iommu, not struct vfio_pci_device.

Reviewed-by: Alex Mastro <amastro@fb.com>
Tested-by: Alex Mastro <amastro@fb.com>
Reviewed-by: Raghavendra Rao Ananta <rananta@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Link: https://lore.kernel.org/r/20251126231733.3302983-14-dmatlack@google.com
Signed-off-by: Alex Williamson <alex@shazbot.org>