8250_pci: Add support for the Digi/IBM PCIe 2-port Adapter

Add support to the 8250 PCI serial driver for the Digi/IBM PCIe 2-port Async EIA-232 Adapter.

Oxford Semiconductor produces a 2/4/8 port UART (OXPCIe952/OXPCIe954/OXPCIe958) chip
called the Tornado, that can be used to create a very simple serial board product.
The kernel sources currently have just 2 vendors using this chip, which is Oxford and Mainpipe.
This new Digi/IBM serial product now uses it as well.

Rather than create a long running comment of vendors using the chip, the one changed comment
in the patch below now just lists "For Oxford Semiconductor Tornado based devices" to be a
more generic comment for all vendors that end up using the Oxford Tornado chip.

Cc: Michael Reed <mreed10@us.ibm.com>
Signed-off-by: Scott Kilau <scottk@digi.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>