pcihp: replace enable|disable_device() with oneliners

enable_device() and disable_device() functions aren't reused anywere,
so replace them with respective oneliners at call sites.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
pcihp: make PCI hotplug mmio handlers indifferent to PCI_HOTPLUG_ADDR

... removes dependency of mmio handler on PCI_HOTPLUG_ADDR.
It will be needed in case of Q35 where base could be different.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
pcihp: make pci_read() mmio calback compatible with legacy ACPI hotplug

due to recent change introduced by:
"pcihp: reduce number of device check events"

'up' field is cleared right after it's read.
This is incompatible with legacy BIOS ACPI code
where PCNF ACPI method reads this field 32 times.

To make pci_read mmio callback compatible with legacy
'up' behavior, pcihp code will need to know in which
mode it runs so move 'use_acpi_pci_hotplug' into
AcpiPciHpState structure and alter register behavior
accordingly.

PS:
And since field 'use_acpi_pci_hotplug' is touched
anyway rename it to reflect its meaning more crearly
to 'legacy_piix' and corresponding property to
'legacy-acpi-pci-hotplug'.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
pcihp: remove unused AcpiPciHpPciStatus.device_present field

Remove now unused 'device_present' field wich was obsoleted by
patch "pcihp: reduce number of device check events"

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
hw:piix4:acpi: reuse pcihp code for legacy PCI hotplug

reduces acpi PCI hotplug code duplication by ~200LOC

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
v3:
 - remove exessive checks for compat mode
 - replace up/down fields of pci_status with corresponding fields
   form AcpiPciHpPciStatus in vmstate wich allow to remove extra
   50 LOC of legacy code
 - move legacy initialization logic to pcihp.c
v2:
 - replace obsolete 'device_present' with 'up' field
 - add/set ACPI_PCIHP_PROP_BSEL to 0 when running in compatibility
   mode with old machine types.