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/x509write_crt.c b/library/x509write_crt.c
index 44b6b17..913b15a 100644
--- a/library/x509write_crt.c
+++ b/library/x509write_crt.c
@@ -33,7 +33,7 @@
 #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 */
 
 void mbedtls_x509write_crt_init(mbedtls_x509write_cert *ctx)