8250: Oxford Semiconductor Devices

Add support for the OxSemi 'Tornado' devices.

Reformatted and reworked a bit by Alan Cox

Signed-off-by: Lee Howard <lee.howard@mainpine.com>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>