tcl/interface: add example of linuxgpiod through dln-2

The USB adapter DLN-2 provides 32 GPIO (beside I2C, SPI, ...).
Use the first 6 GPIO for a SWD/JTAG bitbanging example through
linuxgpiod driver.

Change-Id: I229c2078142ec648fc6430b5d123539045dcfbda
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/5561
Tested-by: jenkins

tcl/interface/dln-2-gpiod.cfg

@@ -0,0 +1,25 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+# Use DLN-2 GPIO through linuxgpiod
+#
+# +-----------+-------------+-------------+
+# | signal    | DLN-2       | gpio offset |
+# +-----------+-------------+-------------+
+# | nSRST     | J3.1  (PA0) | 0           |
+# | TDO       | J3.2  (PA1) | 1           |
+# | TCK/SWCLK | J3.3  (PA2) | 2           |
+# | TMS/SWDIO | J3.4  (PA3) | 3           |
+# | TDI       | J3.5  (PA4) | 4           |
+# | nTRST     | J3.6  (PA5) | 5           |
+# | GND       | J3.12 (GND) |             |
+# +-----------+-------------+-------------+
+
+adapter driver linuxgpiod
+
+linuxgpiod_gpiochip 0
+linuxgpiod_jtag_nums 2 3 4 1
+linuxgpiod_trst_num 5
+linuxgpiod_swd_nums 2 3
+linuxgpiod_srst_num 0
+
+reset_config trst_and_srst separate srst_push_pull