hw/acpi/ich9: Add compat prop to keep HPC bit set for 6.1 machine type

hw/acpi/ich9: Add compat prop to keep HPC bit set for 6.1 machine type

To solve issues [1-2] the Hot Plug Capable bit in PCIe Slots will be
turned on, while the switch to ACPI Hot-plug will be done in the
DSDT table.

Introducing 'x-keep-native-hpc' property disables the HPC bit only
in 6.1 and as a result keeps the forced 'reserve-io' on
pcie-root-ports in 6.1 too.

[1] https://gitlab.com/qemu-project/qemu/-/issues/641
[2] https://bugzilla.redhat.com/show_bug.cgi?id=2006409

Signed-off-by: Julia Suvorova <jusual@redhat.com>
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20211112110857.3116853-3-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>