psa_util: add include asn1write.h in public header

This is mandatory to have support for the error codes defined
in the asn1write.h header file.

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/include/mbedtls/psa_util.h b/include/mbedtls/psa_util.h
index ea0d5bb..87787f1 100644
--- a/include/mbedtls/psa_util.h
+++ b/include/mbedtls/psa_util.h
@@ -16,6 +16,11 @@
 
 #include "psa/crypto.h"
 
+/* ASN1 defines used in the ECDSA conversion functions. */
+#if defined(MBEDTLS_ASN1_WRITE_C) || defined(MBEDTLS_ASN1_PARSE_C)
+#include <mbedtls/asn1write.h>
+#endif
+
 #if defined(MBEDTLS_PSA_CRYPTO_C)
 
 /* Expose whatever RNG the PSA subsystem uses to applications using the
diff --git a/tests/suites/test_suite_psa_crypto_util.function b/tests/suites/test_suite_psa_crypto_util.function
index 2a99073..bf1f88d 100644
--- a/tests/suites/test_suite_psa_crypto_util.function
+++ b/tests/suites/test_suite_psa_crypto_util.function
@@ -1,8 +1,6 @@
 /* BEGIN_HEADER */
-#include <stdint.h>
 #include <test/helpers.h>
 #include <mbedtls/psa_util.h>
-#include <mbedtls/asn1write.h>
 
 enum  {
     ECDSA_RAW_TO_DER = 0,