hw/pci-host/i440fx: Add PCI_HOST_{ABOVE, BELOW}_4G_MEM_SIZE properties

hw/pci-host/i440fx: Add PCI_HOST_{ABOVE, BELOW}_4G_MEM_SIZE properties

Introduce the properties in anticipation of QOM'ification; Q35 has the same
properties.

Note that we want to avoid a "ram size" property in the QOM interface since it
seems redundant to both properties introduced in this change. Thus the removal
of the ram_size parameter. We assume the invariant of both properties to sum up
to "ram size" which is already asserted in pc_memory_init(). Under Xen the
invariant seems to hold as well, so we now also check it there.

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
Message-Id: <20230630073720.21297-15-shentey@gmail.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>