x86 PICs as devices

[ehem]

A major reason behind non-x86 PICs being devices is to utilize the module and newbus infrastructure. This does make x86 the odd one out, so turning the x86 PICs into full devices will likely aid converging the interrupt systems.

Having PICs for all architectures be proper devices allows the interrupt event core use device methods for interrupt callbacks. This shrinks the interrupt event data structures as everything can be done via a single pointer, rather than a pointer for each callback.

If interrupt events could be embedded inside the architecture interrupt structures, struct intr_event could be further shrunk by removing another pointer. The result would make the architecture core <=> event core relationship similar to the PIC <=> architecture core relationship.