Q35 has now ACPI hotplug enabled by default for PCI(e) devices.
As opposed to native PCIe hotplug, guests like Fedora 34
will not assign IO range to pcie-root-ports not supporting
native hotplug, resulting into a regression.

Reproduce by:
    qemu-bin -M q35 -device pcie-root-port,id=p1 -monitor stdio
    device_add e1000,bus=p1
In the Guest OS the respective pcie-root-port will have the IO range
disabled.

Fix it by setting the "reserve-io" hint capability of the
pcie-root-ports so the firmware will allocate the IO range instead.

Acked-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
Message-Id: <20210802090057.1709775-1-marcel@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>