ich9: honour 'enable_tco' property

An 'ICH9-LPC.enable_tco' property has been exposed for a
very long time, but attempts to set it have never been
honoured.

Originally, any user provided 'enable_tco' value was force
replaced by a value passed from the machine type setup
code that was determine by machine type compat properties.

  commit d6b304b
  Author: Eduardo Habkost <ehabkost@redhat.com>
  Date:   Sat Jan 23 14:02:10 2016 -0200

    machine: Remove no_tco field

    The field is always set to zero, so it is not necessary anymore.

After legacy Q35 machine types were deleted in:

  commit 86165b4
  Author: Eduardo Habkost <ehabkost@redhat.com>
  Date:   Sat Jan 23 14:02:09 2016 -0200

    q35: Remove old machine versions

the machine type code ended up just unconditionally passing
'true', all the time, so this was further simplified in

  commit d6b304b
  Author: Eduardo Habkost <ehabkost@redhat.com>
  Date:   Sat Jan 23 14:02:10 2016 -0200

    machine: Remove no_tco field

    The field is always set to zero, so it is not necessary anymore.

  commit 18d6aba
  Author: Eduardo Habkost <ehabkost@redhat.com>
  Date:   Sat Jan 23 14:02:11 2016 -0200

    ich9: Remove enable_tco arguments from init functions

    The enable_tco arguments are always true, so they are not needed
    anymore.

Leaving the ich9_pm_init to just force set 'enable_tco' to true.
This still overrides any user specified property. The initialization
of property defaults should be done when properties are first
registered, rather than during object construction.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20221216125749.596075-6-berrange@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/acpi/ich9.c

@@ -316,8 +316,9 @@ void ich9_pm_init(PCIDevice *lpc_pci, ICH9LPCPMRegs *pm,
 
     pm->smm_enabled = smm_enabled;
 
-    pm->enable_tco = true;
-    acpi_pm_tco_init(&pm->tco_regs, &pm->io);
+    if (pm->enable_tco) {
+        acpi_pm_tco_init(&pm->tco_regs, &pm->io);
+    }
 
     if (pm->use_acpi_hotplug_bridge) {
         acpi_pcihp_init(OBJECT(lpc_pci),
@@ -440,6 +441,7 @@ void ich9_pm_add_properties(Object *obj, ICH9LPCPMRegs *pm)
     pm->s4_val = 2;
     pm->use_acpi_hotplug_bridge = true;
     pm->keep_pci_slot_hpc = true;
+    pm->enable_tco = true;
 
     object_property_add_uint32_ptr(obj, ACPI_PM_PROP_PM_IO_BASE,
                                    &pm->pm_io_base, OBJ_PROP_FLAG_READ);