sparseirq: fix !SMP building, #2

Impact: build fix

make intr_remapping.c to include smp.h, so could use boot_cpu_id there

also remove old change that disabling sparseirq with !SMP

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>