Start testing cf_hmac() for constant flow

Currently this breaks all.sh component test_memsan_constant_flow, just as
expected, as the current implementation is not constant flow.

This will be fixed in the next commit.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/tests/suites/test_suite_ssl.function b/tests/suites/test_suite_ssl.function
index 2eafb2f..f7e3be3 100644
--- a/tests/suites/test_suite_ssl.function
+++ b/tests/suites/test_suite_ssl.function
@@ -118,10 +118,13 @@
                 data[i] = ( i & 0xff ) ^ rec_num;
 
             /* Get the function's result */
+            TEST_CF_SECRET( &in_len, sizeof( in_len ) );
             TEST_ASSERT( 0 == mbedtls_ssl_cf_hmac( &ctx, add_data, sizeof( add_data ),
                                                    data, in_len,
                                                    min_in_len, max_in_len,
                                                    out ) );
+            TEST_CF_PUBLIC( &in_len, sizeof( in_len ) );
+            TEST_CF_PUBLIC( out, out_len );
 
             /* Compute the reference result */
             TEST_ASSERT( 0 == mbedtls_md_hmac_update( &ref_ctx, add_data,