RSA: always use MD light

Note: already auto-enabled in build_info.h

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/tests/suites/test_suite_rsa.function b/tests/suites/test_suite_rsa.function
index a2fe6c8..96fc59b 100644
--- a/tests/suites/test_suite_rsa.function
+++ b/tests/suites/test_suite_rsa.function
@@ -1376,6 +1376,10 @@
 /* BEGIN_CASE depends_on:MBEDTLS_SELF_TEST */
 void rsa_selftest()
 {
+    MD_PSA_INIT();
     TEST_ASSERT(mbedtls_rsa_self_test(1) == 0);
+
+exit:
+    MD_PSA_DONE();
 }
 /* END_CASE */