[SERIAL] Expose 8250_pci setup/removal/suspend/resume functions

Re-jig the setup/removal/suspend/resume of 8250 pci ports so that they
know slightly less about how they're attached to a PCI device.  Expose
this as the new interface for registering PCI serial ports, as well as
the pciserial_board structure and associated flag definitions.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>