iommu/amd: Add early maps for ioapic and hpet

This is needed in a later patch were ioapic_map and hpet_map
entries are created before the slab allocator is initialized
(and thus add_special_device() can't be used).

Reviewed-by: Shuah Khan <shuahkhan@gmail.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>