iommu/amd: Enable Guest Translation before registering devices

IOMMU Guest Translation (GT) feature needs to be enabled before
invalidating guest translations (CMD_INV_IOMMU_PAGES with GN=1).

Currently GT feature is enabled after setting up interrupt handler.
So far it was fine as we were not invalidating guest page table
before this point.

Upcoming series will introduce per device GCR3 table and it will
invalidate guest pages after configuring. Hence move GT feature
enablement to early_enable_iommu().

Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20240205115615.6053-3-vasant.hegde@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>