Improve legacy FreeRTOS license detection

Add new rule and fix a previously failing test

Signed-off-by: Philippe Ombredanne <pombredanne@nexb.com>

Author: pombredanne

src/licensedcode/data/rules/freertos-exception-2.0_5.RULE

@@ -0,0 +1,20 @@
+Any FreeRTOS source code, whether modified or in its original release form, or whether in whole or in part, can only be distributed by you under the terms of the GNU General Public License plus this exception. An independent module is a module which is not derived from or based on FreeRTOS.
+
+EXCEPTION TEXT:
+
+    Clause 1
+
+    Linking FreeRTOS statically or dynamically with other modules is making a combined work based on FreeRTOS. Thus, the terms and conditions of the GNU General Public License cover the whole combination.
+
+    As a special exception, the copyright holder of FreeRTOS gives you permission to link FreeRTOS with independent modules that communicate with FreeRTOS solely through the FreeRTOS API interface, regardless of the license terms of these independent modules, and to copy and distribute the resulting combined work under terms of your choice, provided that
+
+    Every copy of the combined work is accompanied by a written statement that details to the recipient the version of FreeRTOS used and an offer by yourself to provide the FreeRTOS source code (including any modifications you may have made) should the recipient request it.
+
+    The combined work is not itself an RTOS, scheduler, kernel or related product.
+
+    The independent modules add significant and primary functionality to FreeRTOS and do not merely extend the existing functionality already present in FreeRTOS.
+
+    Clause 2
+
+    FreeRTOS may not be used for any competitive or comparative purpose, including the publication of any form of run time or compile time metric, without the express permission of Real Time Engineers Ltd. (this is the norm within the industry and is intended to ensure information accuracy).
+

src/licensedcode/data/rules/freertos-exception-2.0_5.yml

@@ -0,0 +1,2 @@
+license_expression: gpl-2.0 WITH freertos-exception-2.0
+is_license_notice: yes

tests/licensedcode/data/more_licenses/tests/SPDX/freertos-exception-2.0.yml

@@ -1,4 +1,2 @@
 license_expressions:
-  - avisynth-c-interface-exception
-  - freertos-exception-2.0
-  - gpl-1.0-plus
+  - gpl-2.0 WITH freertos-exception-2.0