x86: Move acpi_table header to main include/ directory

This file is potentially useful to other architectures saddled with ACPI
so move most of its contents to a common location.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Wolfgang Wallner <wolfgang.wallner@br-automation.com>