interrupt: add separate pre- and post-eoi interrupt handler

kvm's pv_eoi functionality fails if any vmexits are taken before the EOI
(likely due to a bug).  Work around this by deferring the handler until after
the interrupt has been EOIed.  Since level-triggered interrupts must be acked
at the device level prior to the EOI, add an additional handler to be called
prior to the EOI.