hw/i386: make IOMMUs configurable via default-configs/

Allow distributions to disable the Intel and/or AMD IOMMU devices.

Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
3 files changed