ACPI: Use valid link to the ACPI specification

Currently, acpi.info is an invalid link to access ACPI specification,
the new valid link is https://uefi.org/specifications.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>