ext,tests: Make return code based on test results

This patch also fixes a spelling mistake.

Change-Id: I8635216e512c10913a9cda54541d7e31e0d22a40
Signed-off-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17450
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>

ext/testlib/result.py

@@ -58,7 +58,7 @@ class _CommonMetadataMixin:
         self._metadata.result = result
 
     @property
-    def unsucessful(self):
+    def unsuccessful(self):
         return self._metadata.result.value != state.Result.Passed