ANDROID: pkvm: x86: Fix IOMMU MMIO register access issue from host VM

Previously only 4KB IOMMU drhd region was ioremapped and therefore
prevented accessing registers above 4KB. Drop overly limiting drhd
region remapping and rely on previous, correct remapping of IOMMU
driver which was done before pkvm deprivilege.

Bug: 436617723
Upstream-Task: 402758258

Fix: Reuse MMIO register space configured by IOMMU driver
(before kernel deprivilege) instead of recalculating remap space.
Change-Id: I63f4640f084a2d5447680b87f4ec52ce248d5fd4
Signed-off-by: Jason Le <jason.v.le@intel.corp-partner.google.com>