ACPI: tables: Fix the stale comments for acpi_locate_initial_tables()

sdt_entry[] is long gone by commit ceb6c468 ("ACPICA: Remove
duplicate table manager"), update the comments to avoid confusion.

Signed-off-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>