x86: Prevent from missing the FADT chaining

Recent approach with FADT writer shows that there is
a room for subtle errors. Prevent this from happening
again by introducing acpi_add_fadt() helper.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
5 files changed