PEM: always use MD light

Note: PEM_PARSE already auto-enables MD_LIGHT in build_info.h

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/tests/suites/test_suite_pem.function b/tests/suites/test_suite_pem.function
index 25b66f8..9546614 100644
--- a/tests/suites/test_suite_pem.function
+++ b/tests/suites/test_suite_pem.function
@@ -44,6 +44,8 @@
     size_t pwd_len = strlen(pwd);
     const unsigned char *buf;
 
+    MD_PSA_INIT();
+
     mbedtls_pem_init(&ctx);
 
     ret = mbedtls_pem_read_buffer(&ctx, header, footer, (unsigned char *) data,
@@ -60,5 +62,6 @@
 
 exit:
     mbedtls_pem_free(&ctx);
+    MD_PSA_DONE();
 }
 /* END_CASE */