library/tests: replace md_psa.h with psa_util.h as include file for MD conversion

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/library/ssl_cookie.c b/library/ssl_cookie.c
index ee81eb4..2772cac 100644
--- a/library/ssl_cookie.c
+++ b/library/ssl_cookie.c
@@ -24,7 +24,7 @@
 #include <string.h>
 
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
-#include "md_psa.h"
+#include "mbedtls/psa_util.h"
 /* Define a local translating function to save code size by not using too many
  * arguments in each translating place. */
 static int local_err_translation(psa_status_t status)