tty: Add support for the WCH384 4S multi-IO card

WCH384 4S board is a PCI-E card with 4 DB9 COM ports detected as
Serial controller: Device 1c00:3470 (rev 10) (prog-if 05 [16850])

Signed-off-by: Sergej Pupykin <ml@sergej.pp.ru>
Acked-by: Zany Yan <sirlight@cox.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>