PCI: Simplify size1 assignment logic

In pbus_size_io() and pbus_size_mem(), a complex ?: operation is performed
to set size1.  Decompose this so it's easier to read.

In the case of pbus_size_mem(), simply initializing size1 to zero ensures
the size1 checks work as expected.

Link: https://lore.kernel.org/r/20241216175632.4175-4-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>