USB: add driver for the USB debug devices

It's a simple usb-serial driver that just creates a tty device to read
and write from.

Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/serial/Makefile b/drivers/usb/serial/Makefile
index a5047dc..61166ad 100644
--- a/drivers/usb/serial/Makefile
+++ b/drivers/usb/serial/Makefile
@@ -18,6 +18,7 @@
 obj-$(CONFIG_USB_SERIAL_CP2101)			+= cp2101.o
 obj-$(CONFIG_USB_SERIAL_CYBERJACK)		+= cyberjack.o
 obj-$(CONFIG_USB_SERIAL_CYPRESS_M8)		+= cypress_m8.o
+obj-$(CONFIG_USB_SERIAL_DEBUG)			+= usb_debug.o
 obj-$(CONFIG_USB_SERIAL_DIGI_ACCELEPORT)	+= digi_acceleport.o
 obj-$(CONFIG_USB_SERIAL_EDGEPORT)		+= io_edgeport.o
 obj-$(CONFIG_USB_SERIAL_EDGEPORT_TI)		+= io_ti.o