tcl/interface/ftdi: Add config for Tigard board

tcl/interface/ftdi: Add config for Tigard board

Tigard[1] is an FT2232H-based development tool designed for ease of use
with many different protocols and targets. It includes a JTAG header
wired to channel B, with labeled pins for the four required signals as
well as nTRST and nSRST, which are connected through an output buffer to
BDBUS4 and BDBUS5 respectively.

Add an interface config for Tigard. I wrote it by referencing the Tigard
schematic and tested it by debugging a couple of RISC-V development
boards.

[1] https://github.com/tigard-tools/tigard

Signed-off-by: Thomas Hebb <tommyhebb@gmail.com>
Change-Id: I34df9f72538ba1e40ad53b568c9cdca96ae4b082
Reviewed-on: https://review.openocd.org/c/openocd/+/6952
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>