Add a tool to generate a picture of the current DAPM state for a sound
card.

dapm-graph is inspired by vizdapm which used to be published on a Wolfson
Micro git repository now disappeared, and has a few forks around:

  https://github.com/mihais/asoc-tools
  https://github.com/alexandrebelloni/asoc-tools

dapm-graph is a full reimplementation with several improvements while still
being a self-contained shell script:

Improvements to rendered output:
 - shows the entire card, not one component hierarchy only
 - each component is rendered in a separate box
 - shows widget on/off status based on widget information alone (the
   original vizdapm propagates the "on" green colour to the first input
   widget)
 - use bold line and gray background and not only green/red line to show
   on/off status (for the color blind)

Improvements for embedded system developers:
 - remote mode: get state of remote device (possibly with minimal rootfs)
   via SSH, but parsing locally for faster operation
 - compatible with BusyBox shell, not only bash

Usability improvements:
 - flexible command line (uses getopts for parsing)
 - detailed help text
 - flag to enable detailed debug logging
 - graphviz output format detected from file extension, not hard coded
 - a self-contained shell script

Usage is designed to be simple:

  dapm-grpah -c CARD                  - get state from debugfs for CARD
  dapm-grpah -c CARD -r REMOTE_TARGET - same, but remotely via SSH
  dapm-grpah -d STATE_DIR             - from a local copy of the debugfs
                                        tree for a card

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20240416-vizdapm-ng-v1-3-5d33c0b57bc5@bootlin.com
Signed-off-by: Mark Brown <broonie@kernel.org>