iommu/amd: Add support for higher 64-bit IOMMU Control Register

Currently, the driver only supports lower 32-bit of IOMMU Control register.
However, newer AMD IOMMU specification has extended this register
to 64-bit. Therefore, replace the accessing API with the 64-bit version.

Cc: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>