hwsim: Include terminating 0 byte in radio name attribute

The kernel expects the radio name attribute to include the string's zero
byte.  Things may still work without this if there is padding after the
attribute.

This has been now patched and the zero byte will be optional when that
patch makes its way through different trees.

tools/hwsim.c

@@ -821,7 +821,7 @@ static void hwsim_ready(void *user_data)
 
 		if (radio_name_attr)
 			l_genl_msg_append_attr(msg, HWSIM_ATTR_RADIO_NAME,
-						strlen(radio_name_attr),
+						strlen(radio_name_attr) + 1,
 							radio_name_attr);
 
 		if (no_vif_attr)