backends/iommufd: Add a helper to invalidate user-managed HWPT

backends/iommufd: Add a helper to invalidate user-managed HWPT

This helper passes cache invalidation request from guest to invalidate
stage-1 page table cache in host hardware.

Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250604062115.4004200-2-zhenzhong.duan@intel.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>