8250_pci: add the OXCB950 chip to the 8250 PCI driver.

This adds support for the following serial controller chip:
Oxford Semiconductor OXCB950 for PCI Cardbus interface
http://www.transdimension.com/products/serial/OXCB950.html

on this card:
ExSys EX-1370 1 port high-speed serial card for ExpressCard/34 slot

Signed-off-by: Andre Przywara <andre.przywara@amd.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>