serial: quatech: add the other serial identifiers and preliminary control code

Jonathan Woithe posted an out of tree enabler/control module for these
cards.  Lift the relevant identifiers and put them in the 8250_pci driver
along with code used to control custom registers on these cards.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Jonathan Woithe <jwoithe@just42.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>