serial/8250: Add support for NI-Serial PXI/PXIe+485 devices

Add support for NI-Serial PXIe-RS232, PXI-RS485 and PXIe-RS485 devices.

Signed-off-by: Je Yen Tam <je.yen.tam@ni.com>
Link: https://lore.kernel.org/r/20190726074012.2590-1-je.yen.tam@ni.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>