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/x509_crt.c b/library/x509_crt.c
index 4e7672e..84b92a8 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -35,7 +35,7 @@
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
 #include "psa/crypto.h"
 #include "psa_util_internal.h"
-#include "md_psa.h"
+#include "mbedtls/psa_util.h"
 #endif /* MBEDTLS_USE_PSA_CRYPTO */
 #include "pk_internal.h"