ACPI: tables: Add AEST to the list of known table signatures

Add AEST to the list of known ACPI table signatures to allow the
kernel to recognize it when upgrading tables via initrd.

Signed-off-by: Shuuichirou Ishii <ishii.shuuichir@fujitsu.com>
Acked-by: Hanjun Guo <guohanjun@huawei.com>
[ rjw: New subject and changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>