openocd: remove cable file for built-in ZC706 JTAG

This typically crappy JTAG adapter just doesn't work.

openocd/digilent_jtag_smt2_nc.cfg

@@ -1,18 +0,0 @@
-#
-# Digilent JTAG-SMT2-NC
-#
-# http://store.digilentinc.com/jtag-smt2-nc-surface-mount-programming-module/
-# https://reference.digilentinc.com/_media/jtag_smt2nc/jtag-smt2-nc_rm.pdf
-#
-# Based on reference sheet (above) and Xilinx KCU105 schematics
-# https://www.xilinx.com/products/boards-and-kits/kcu105.html#documentation
-#
-# Note that the digilent_jtag_smt2 layout does not work and hangs while
-# the ftdi_device_desc from digilent_hs2 is wrong.
-
-interface ftdi
-ftdi_device_desc "Digilent USB Device"
-ftdi_vid_pid 0x0403 0x6014
-ftdi_channel 0
-ftdi_layout_init 0x00e8 0x60eb
-ftdi_layout_signal nSRST -data 0x2000