Staging: quatech_usb2: vendor implementation of set_termios method

This patch imports the implementation of the set_termios method from the
vendor driver into the staging driver. The common terminal setting
changes should be supported.

Signed-off-by: Richard Ash <richard@audacityteam.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>