adapter: Rework parallel port driver

Make the driver more flexible and define adapter-specific configurations
in Tcl instead of C using the adapter GPIO subsystem.

The rework also includes coding style fixes and improvements of the
documentation. All modifications are done such that backwards
compatibility is ensured.

Tested with Olimex ARM-JTAG cable [1] and APM32F103 target device on
Linux and FreeBSD. The driver works on Linux using direct I/O and PPDEV.
On FreeBSD, only PPDEV works. The build with direct I/O already failed
before the patch. This problem will be fixed in a subsequent patch.

The patch is not tested on Windows because there is no documentation
for it.

[1] https://www.olimex.com/Products/ARM/JTAG/ARM-JTAG/

Change-Id: Ib671d52a919eaf2959cf6365f2c8004257ae074c
Signed-off-by: Marc Schink <dev@zapb.de>
Reviewed-on: https://review.openocd.org/c/openocd/+/8943
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Tested-by: jenkins

tcl/interface/parport/dlc5.cfg

@@ -1,17 +1,16 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 
-#
 # Xilinx Parallel Cable III 'DLC 5' (and various clones)
-#
-# http://www.xilinx.com/itp/xilinx4/data/docs/pac/appendixb.html
-#
-
-if { [info exists PARPORTADDR] } {
-   set _PARPORTADDR $PARPORTADDR
-} else {
-   set _PARPORTADDR 0
-}
 
 adapter driver parport
-parport port $_PARPORTADDR
-parport cable dlc5
+
+adapter gpio tdo 13 -exit-inactive
+adapter gpio tms 4 -exit-inactive
+adapter gpio tck 3 -exit-inactive
+adapter gpio tdi 2 -exit-inactive
+
+# Non-JTAG signal that is only necessary for the functionality of the adapter.
+# For details, refer to the documentation of the adapter.
+adapter gpio user0 6 -init-active -exit-active
+
+transport select jtag