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/cli.c b/cli.c
index 82723fd..6a0cbe1 100644
--- a/cli.c
+++ b/cli.c
@@ -27,6 +27,8 @@
 } commands[] = {
 	{ "mem",		flashprog_classic_main },
 	{ "memory",		flashprog_classic_main },
+	{ "cfg",		flashprog_config_main },
+	{ "config",		flashprog_config_main },
 };
 
 static void usage(const char *const name)
@@ -35,6 +37,7 @@
 	fprintf(stderr, "\nWhere <command> can be\n\n"
 			" mem[ory]                 Standard memory operations\n"
 			"                          (read/erase/write/verify)\n"
+			" cfg|config               Status/config register operations\n"
 			"\n"
 			"The default is 'memory'. See `%s <command> --help`\n"
 			"for further instructions.\n\n", name);