iommu/amd: Rearrange GCR3 table setup code

iommu/amd: Rearrange GCR3 table setup code

Consolidate GCR3 table related code in one place so that its easy
to maintain.

Note that this patch doesn't move __set_gcr3/__clear_gcr3. We are moving
GCR3 table from per domain to per device. Following series will rework
these functions. During that time I will move these functions as well.

No functional changes intended.

Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20240205115615.6053-9-vasant.hegde@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>