cfg: Add interface config for Dangerous Prototypes BusBlaster

cfg: Add interface config for Dangerous Prototypes BusBlaster

The BusBlaster from Dangerous Prototypes is based on the FTDI FT2232H IC.
It has a CPLD between the FT2232H and the JTAG header allowing it to
emulate various debugger types. It comes configured as a JTAGkey compatible
device.

Change-Id: Iab56907bf67ded87001e628d93012f1e16287d90
Signed-off-by: Richard Barlow <richard@richardbarlow.co.uk>
Reviewed-on: http://openocd.zylin.com/53
Tested-by: jenkins
Reviewed-by: Peter Stuge <peter@stuge.se>