PCI: Fix finding bridge window in pci_reassign_bridge_resources()

pci_reassign_bridge_resources() walks upwards in the PCI bus hierarchy,
locates the relevant bridge window on each level using flags check, and
attempts to release the bridge window. The flags-based check is fragile due
to various fallbacks in the bridge window selection logic. As such, the
algorithm might not locate the correct bridge window.

Refactor pci_reassign_bridge_resources() to determine the correct bridge
window using pbus_select_window(), which contains logic to handle all
fallback cases correctly. Change function prefix to pbus as it now inputs
struct bus and resource for which to locate the bridge window.

The main purpose is to make bridge window selection logic consistent across
the entire PCI core (one step at a time). While this technically also fixes
the commit 8bb705e3 ("PCI: Add pci_resize_resource() for resizing
BARs") making the bridge window walk algorithm more robust, the normal
setup having a 64-bit resizable BAR underneath bridge(s) with 64-bit
prefetchable windows does not need to use any fallbacks. As such, the
practical impact is low (requiring BAR resize use case and a non-typical
bridge device).

The way to detect if unrelated resource failed again is left to use the
type based approximation which should not behave worse than before.

Fixes: 8bb705e3 ("PCI: Add pci_resize_resource() for resizing BARs")
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20250829131113.36754-14-ilpo.jarvinen@linux.intel.com