checkpatch.pl: Add check for defining CONFIG_CMD_xxx via config files

All of our cmds have a Kconfig entry.  Making enabling a CMD via the
config file an error to checkpatch.pl.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 17d4182..edba365 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -2267,6 +2267,12 @@
 		WARN("PREFER_IF",
 		     "Use 'if (IS_ENABLED(CONFIG...))' instead of '#if or #ifdef' where possible\n" . $herecurr);
 	}
+
+	# use defconfig to manage CONFIG_CMD options
+	if ($line =~ /\+\s*#\s*(define|undef)\s+(CONFIG_CMD\w*)\b/) {
+		ERROR("DEFINE_CONFIG_CMD",
+		      "All commands are managed by Kconfig\n" . $herecurr);
+	}
 }
 
 sub process {