usb-serial: Use ftdi_sio driver for RATOC REX-USB60F

This patch reverts 57833ea6
("usb-serial: pl2303: add support for RATOC REX-USB60F") and adds
support for the device to ftdi_sio driver.

Cc: Akira Tsukamoto <akirat@rd.scei.sony.co.jp>
Cc: stable <stable@kernel.org>
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>