[SERIAL] Overhaul 8250_pci.c

- Add local copy of flags for describing port characteristics.
- Add "quirk" handling to sort out board-specific initialisation,
  per-port setup, and finalisation.
- Remove quirk information from struct pci_board array, thereby
  making entries more generic.
- Initialise struct pci_board array using explicit indicies -
  adding to the readability, and making sure that the right entries
  are in the correct location in the table.
- Ensure we tell the serial layer to claim resources, and share
  interrupts.  PCI interrupts are sharable, and need to be so that
  multi-function cardbus cards will work.
- Only remap each PCI memory BAR once.
- Add pci serial driver to the tty devclass (this requires the patch
  to make tty_io.c register the tty devclass early.)

Tested by CaT and myself.