hpet source code cleanup

Signed-off-by: Lukas Humbel <lukas.humbel@inf.ethz.ch>

Driver can now trigger and receive interrupts through FSB and I/O APIC mapping

Signed-off-by: Rana Afifi <afrana@student-ethz.ch>

ACPI: towards handling all MADT table entries

Signed-off-by: Reto Achermann <reto.achermann@inf.ethz.ch>