PCI/portdrv: Move private things to portdrv.c

PCI/portdrv: Move private things to portdrv.c

Previously several things used by portdrv_core.c and portdrv_pci.c were
shared by defining them in portdrv.h.  Now that portdrv_core.c and
portdrv_pci.c have been squashed, move things that can be private into
portdrv.c.  No functional change intended.

Link: https://lore.kernel.org/r/20221019204127.44463-3-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>