soc/intel/alderlake/acpi.c: Don't look up coreboot CPU index

soc/intel/alderlake/acpi.c: Don't look up coreboot CPU index

The coreboot CPU index for a lapic is arbitrary: it depends on which
CPU obtains a spinlock first. Simply using an increasing index will
result in consistent ACPI tables across each boot.

Change-Id: Iaaaef213b32b33e3ec9f4874d576896c2335211c
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/69510
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>