hw/i386/intel_iommu: Remove IntelIOMMUState::buggy_eim field

hw/i386/intel_iommu: Remove IntelIOMMUState::buggy_eim field

The IntelIOMMUState::buggy_eim boolean was only set in
the hw_compat_2_7[] array, via the 'x-buggy-eim=true'
property. We removed all machines using that array, lets
remove that property, simplifying vtd_decide_config().

Reviewed-by: Mark Cave-Ayland <mark.caveayland@nutanix.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20260108033051.777361-26-zhao1.liu@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>