PCI/portdrv: Squash into portdrv.c

PCI/portdrv: Squash into portdrv.c

Squash portdrv_core.c and portdrv_pci.c into portdrv.c to make it easier to
find things.  The whole thing is less than 1000 lines, and it's a pain to
bounce back and forth between two files.

Several portdrv_core.c functions were non-static because they were
referenced from portdrv_pci.c.  Make them static since they're now all in
portdrv.c.

No functional change intended.

Link: https://lore.kernel.org/r/20221019204127.44463-2-helgaas@kernel.org
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>