hw/pci-host/i440fx: Inline sysbus_add_io()

sysbus_add_io() just wraps memory_region_add_subregion() while also
obscuring where the memory is attached. So use
memory_region_add_subregion() directly and attach it to the existing
memory region s->bus->address_space_io which is set as an alias to
get_system_io() by the pc machine.

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20230213162004.2797-2-shentey@gmail.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

hw/pci-host/i440fx.c

@@ -27,6 +27,7 @@
 #include "qemu/range.h"
 #include "hw/i386/pc.h"
 #include "hw/pci/pci.h"
+#include "hw/pci/pci_bus.h"
 #include "hw/pci/pci_host.h"
 #include "hw/pci-host/i440fx.h"
 #include "hw/qdev-properties.h"
@@ -217,10 +218,10 @@ static void i440fx_pcihost_realize(DeviceState *dev, Error **errp)
     PCIHostState *s = PCI_HOST_BRIDGE(dev);
     SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
 
-    sysbus_add_io(sbd, 0xcf8, &s->conf_mem);
+    memory_region_add_subregion(s->bus->address_space_io, 0xcf8, &s->conf_mem);
     sysbus_init_ioports(sbd, 0xcf8, 4);
 
-    sysbus_add_io(sbd, 0xcfc, &s->data_mem);
+    memory_region_add_subregion(s->bus->address_space_io, 0xcfc, &s->data_mem);
     sysbus_init_ioports(sbd, 0xcfc, 4);
 
     /* register i440fx 0xcf8 port as coalesced pio */