cli: Add new `config' CLI for status/config registers

TBD

For instance, the quad-enable bit can then be queried like this:

  $ flashprog config -p ch341a_spi --get quad-enable

TODO: Write a manpage once the syntax is agreed upon.

Change-Id: I6b9d26c67e6ad65be5df367d2db7942bb98f27ac
Signed-off-by: Nico Huber <nico.h@gmx.de>
diff --git a/meson.build b/meson.build
index e8dd525..c871ad9 100644
--- a/meson.build
+++ b/meson.build
@@ -606,6 +606,7 @@
     'flashprog',
     files(
       'cli.c',
+      'cli_config.c',
       'cli_classic.c',
       'cli_common.c',
       'cli_output.c',