asn1: use the new symbol to guard dependencies of ECDSA conversion functions

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/include/mbedtls/asn1.h b/include/mbedtls/asn1.h
index 3c3bfad..ff019f4 100644
--- a/include/mbedtls/asn1.h
+++ b/include/mbedtls/asn1.h
@@ -197,7 +197,8 @@
 }
 mbedtls_asn1_named_data;
 
-#if defined(MBEDTLS_ASN1_PARSE_C) || defined(MBEDTLS_X509_CREATE_C)
+#if defined(MBEDTLS_ASN1_PARSE_C) || defined(MBEDTLS_X509_CREATE_C) || \
+    defined(MBEDTLS_PSA_UTIL_HAVE_ECDSA)
 /**
  * \brief       Get the length of an ASN.1 element.
  *              Updates the pointer to immediately behind the length.
@@ -244,7 +245,7 @@
 int mbedtls_asn1_get_tag(unsigned char **p,
                          const unsigned char *end,
                          size_t *len, int tag);
-#endif /* MBEDTLS_ASN1_PARSE_C || MBEDTLS_X509_CREATE_C */
+#endif /* MBEDTLS_ASN1_PARSE_C || MBEDTLS_X509_CREATE_C || MBEDTLS_PSA_UTIL_HAVE_ECDSA */
 
 #if defined(MBEDTLS_ASN1_PARSE_C)
 /**