lapic timer: Finish the lapic timer support
- Add lapic_timer_process_oncpu(), which fires per-cpu systimer queue.
- Add lapic_timer_intr_reload(), which restart/start lapic timer.
- Change cputimer_intr_reload to function pointer, so it could be
overridden when needed. It is original cputimer_intr_reload function
on amd64 and vkernel. On i386, APIC initialization will set it to
lapic_timer_intr_reload if lapic_timer_enable tunable is set to 1,
else i8254_intr_reload (origial cputimer_intr_reload) will be used.
- If lapic_timer_enable is 1, then don't try to register "clk" interrupt
handler at all.
As of this commit, lapic timer support is done. It is not enabled by
default, set 'hw.lapci_timer_enable' to enable it.