PCI: Stop over-estimating bridge window size

PCI: Stop over-estimating bridge window size

New way to calculate the bridge window head alignment produces tight-fit,
that is, it does not leave any gaps between the resources.  Similarly,
relaxed tail alignment does not leave extra tail room.

Start to use bridge window calculation that does not over-estimate the size
of the required window.

pbus_upstream_space_available() can be removed.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Malte Schröder <malte+lkml@tnxip.de>
Link: https://patch.msgid.link/20251219174036.16738-4-ilpo.jarvinen@linux.intel.com