iommu/amd: Remove unused amd_iommus variable

protection_domain structure is updated to use xarray to track the IOMMUs
attached to the domain. Now domain flush code is not using amd_iommus.
Hence remove this unused variable.

Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Joerg Roedel <jroedel@suse.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20241030063556.6104-6-vasant.hegde@amd.com


Signed-off-by: Joerg Roedel <jroedel@suse.de>