stlink: add usb pid for v2.1 without mass storage device

stlink: add usb pid for v2.1 without mass storage device

New version of ST-Link/V2.1 without mass storage device.
From debug point of view, it is compatible with existing ST-Link/V2.1
It uses a new USB PID because the USB endpoints and interfaces are
different from usual ST-Link/V2.1

Add the new PID in the driver, in the tcl interface script and in the
udev configuration script.

Change-Id: Id2e1b5a5d0347c5d951a86a9cdb76be52cfd4ea3
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/4702
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>