LinuxKPI: Exclude linux/acpi.h content on non-ACPI archs.

LinuxKPI ACPI support is based on FreeBSD import of ACPICA which can be
compiled only on aarch64, amd64 and i386. Ifdef-out broken parts on our
side to avoid patching of vendor code.

This fixes drm-devel-kmod build on powerpc64(le).

Reported by: pkubaj