check length of private key components before setting

the card functions only accepts key components of correct size
so here we add 0 before if they're shorter (usually one byte shorter)
thus fixing the issue where the card returned 6f00

tool/util.c

@@ -203,3 +203,15 @@ int get_object_id(enum enum_slot slot) {
   }
   return object;
 }
+
+bool set_component_with_len(unsigned char **in_ptr, const BIGNUM *bn, int element_len) {
+  int real_len = BN_num_bytes(bn);
+  *in_ptr += set_length(*in_ptr, element_len);
+  if(real_len > element_len) {
+    return false;
+  }
+  memset(*in_ptr, 0, (size_t)(element_len - real_len));
+  *in_ptr += element_len - real_len;
+  *in_ptr += BN_bn2bin(bn, *in_ptr);
+  return true;
+}