PCI: Fix old_size lower bound in calculate_iosize() too

PCI: Fix old_size lower bound in calculate_iosize() too

Commit 903534fa7d30 ("PCI: Fix resource double counting on remove &
rescan") fixed double counting of mem resources because of old_size being
applied too early.

Fix a similar counting bug on the io resource side.

Link: https://lore.kernel.org/r/20241216175632.4175-6-ilpo.jarvinen@linux.intel.com
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Xiaochun Lee <lixc17@lenovo.com>