util/lint: Update license linter, make stable version

- Split the script up to make it easier to update and read.
- Check for multiple different license strings. Not all files are GPL
licensed.
- Don't validate 0 length files
- Update list of files to exclude from the license header check.
- Add command line option to set directories to check

- Add stable version to check a few directories that are fixed.  This
just calls the non-stable version with the directories to check.

Change-Id: I90d4e93a20b4e1638ce4f43f8acbee72dc588625
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/12909
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

util/lint/lint-stable-000-license-headers

@@ -0,0 +1,18 @@
+#!/bin/sh
+# This file is part of the coreboot project.
+#
+# Copyright (C) 2016 Google Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+#
+# DESCR: Check that files have license headers
+
+util/lint/lint-000-license-headers "src/arch src/acpi src/superio src/ec src/commonlib"