Ensure mutex test mutex gets free'd

Signed-off-by: Paul Elliott <paul.elliott@arm.com>
diff --git a/tests/include/test/helpers.h b/tests/include/test/helpers.h
index ba117fb..4708df1 100644
--- a/tests/include/test/helpers.h
+++ b/tests/include/test/helpers.h
@@ -240,10 +240,18 @@
 #endif
 
 #if defined(MBEDTLS_TEST_MUTEX_USAGE)
-/** Permanently activate the mutex usage verification framework. See
- * threading_helpers.c for information. */
+/**
+ *  Activate the mutex usage verification framework. See threading_helpers.c for
+ *  information.
+ *  */
 void mbedtls_test_mutex_usage_init(void);
 
+/**
+ *  Deactivate the mutex usage verification framework. See threading_helpers.c
+ *  for information.
+ */
+void mbedtls_test_mutex_usage_end(void);
+
 /** Call this function after executing a test case to check for mutex usage
  * errors. */
 void mbedtls_test_mutex_usage_check(void);