Move testing of mbedtls_aria_free() to separate test

The test that mbedtls_aria_free() accepts NULL parameters
can be performed even if MBEDTLS_CHECK_PARAMS is unset, but
was previously included in the test case aria_invalid_params()
which is only executed if MBEDTLS_CHECK_PARAMS is set.
diff --git a/tests/suites/test_suite_aria.function b/tests/suites/test_suite_aria.function
index 8ceb5bb..6e29e53 100644
--- a/tests/suites/test_suite_aria.function
+++ b/tests/suites/test_suite_aria.function
@@ -16,6 +16,13 @@
  * END_DEPENDENCIES
  */
 
+/* BEGIN_CASE */
+void aria_valid_param( )
+{
+    TEST_VALID_PARAM( mbedtls_aria_free( NULL ) );
+}
+/* END_CASE */
+
 /* BEGIN_CASE depends_on:MBEDTLS_CHECK_PARAMS:!MBEDTLS_PARAM_FAILED_ALT */
 void aria_invalid_param( )
 {
@@ -27,7 +34,6 @@
     size_t iv_off = 0;
 
     TEST_INVALID_PARAM( mbedtls_aria_init( NULL ) );
-    TEST_VALID_PARAM( mbedtls_aria_free( NULL ) );
 
     TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ARIA_BAD_INPUT_DATA,
                             mbedtls_aria_setkey_enc( NULL, key,