hw/intc/apic: Remove APICCommonState::legacy_instance_id field

The APICCommonState::legacy_instance_id boolean was only set
in the pc_compat_2_6[] array, via the 'legacy-instance-id=on'
property. We removed all machines using that array, lets remove
that property, simplifying apic_common_realize().

Because instance_id is initialized as initial_apic_id, we can
not register vmstate_apic_common directly via dc->vmsd.

Reviewed-by: Mark Cave-Ayland <mark.caveayland@nutanix.com>
Reviewed-by: Thomas Huth <thuth@redhat.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/20260108033051.777361-18-zhao1.liu@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/intc/apic_common.c

@@ -276,9 +276,6 @@ static void apic_common_realize(DeviceState *dev, Error **errp)
         info->enable_tpr_reporting(s, true);
     }
 
-    if (s->legacy_instance_id) {
-        instance_id = VMSTATE_INSTANCE_ID_ANY;
-    }
     vmstate_register_with_alias_id(NULL, instance_id, &vmstate_apic_common,
                                    s, -1, 0, NULL);
 
@@ -395,8 +392,6 @@ static const Property apic_properties_common[] = {
     DEFINE_PROP_UINT8("version", APICCommonState, version, 0x14),
     DEFINE_PROP_BIT("vapic", APICCommonState, vapic_control, VAPIC_ENABLE_BIT,
                     true),
-    DEFINE_PROP_BOOL("legacy-instance-id", APICCommonState, legacy_instance_id,
-                     false),
 };
 
 static void apic_common_get_id(Object *obj, Visitor *v, const char *name,

include/hw/i386/apic_internal.h

@@ -187,7 +187,6 @@ struct APICCommonState {
     uint32_t vapic_control;
     DeviceState *vapic;
     hwaddr vapic_paddr; /* note: persistence via kvmvapic */
-    bool legacy_instance_id;
     uint32_t extended_log_dest;
 };