amd64/acpica/acpi_wakeup.c: do not store to WARMBOOT_OFF in efi_boot case

[kib]

Summary

Split acpi_wakeup_cpus() into acpi_wakeup_cpus_bios() and
acpi_wakeup_cpus_efi().  The former needs to manipulate zero page and
CMOS state, the later does not.

Referenced commit left the write to WARMBOOT_OFF in case of
acpi_wakeup_ap() failed.

Fixes:  e99255c8a6cae324aeede7f5013d080a2d361e3f

[kib]

Remove blank line

[kib]

And remove stale comment