tcl: Add support for the Digilent Nexys Video board

* https://store.digilentinc.com/nexys-video-artix-7-fpga-trainer-board-for-multimedia-applications/
* https://reference.digilentinc.com/_media/nexys-video:nexys_video_sch.pdf

The Nexys Video board has FTDI FT2232 whose channel B is connected to
Artix-7 FPGA's JTAG pins, and can be supported by OpenOCD's
ftdi interface. Tested to be working fine on real hardware.

Change-Id: I2996166dc8c2b6c08a9390958adfcdec8fc2bd37
Signed-off-by: Rohit Singh <rohit91.2008@gmail.com>
Signed-off-by: Marc Schink <dev@zapb.de>
Reviewed-on: http://openocd.zylin.com/4364
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

tcl/board/digilent_nexys_video.cfg

@@ -0,0 +1,26 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+# Digilent Nexys Video with Xilinx Artix-7 FPGA
+# https://reference.digilentinc.com/programmable-logic/nexys-video/start
+
+adapter driver ftdi
+adapter speed 30000
+
+ftdi_device_desc "Digilent USB Device"
+ftdi_vid_pid 0x0403 0x6010
+
+# channel 0 is dedicated for Digilent's DPTI Interface
+# channel 1 is used for JTAG
+ftdi_channel 1
+
+# just TCK TDI TDO TMS, no reset
+ftdi_layout_init 0x0088 0x008b
+reset_config none
+
+# Enable sampling on falling edge for high JTAG speeds.
+ftdi_tdo_sample_edge falling
+
+transport select jtag
+
+source [find cpld/xilinx-xc7.cfg]
+source [find cpld/jtagspi.cfg]