iommu/amd: Remove the unused struct amd_ir_data.ref

iommu/amd: Remove the unused struct amd_ir_data.ref

Since the amd_iommu_update_ga() has been switched to use the
modify_irte_ga() helper function to update the IRTE, the parameter
is no longer needed.

Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Suggested-by: Vasant Hegde <vasant.hegde@amd.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Link: https://lore.kernel.org/r/20230530141137.14376-3-suravee.suthikulpanit@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>