acpi: Use sleep types defined in sys/power.h
This is as opposed to using ACPI sleep states directly
(ACPI_STATE_S*). We now use POWER_STYPE_* added in D52036.
This is in preparation for adding support for s2idle, which is not an
ACPI sleep state, but needs to be handled specially by
acpi_EnterSleepState.
Reviewed by: cy
Approved by: cy
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D52705
Event: EuroBSDcon 2025 Devsummit