KVM: Replace kvm_lapic with kvm_vcpu in ioapic/lapic interface

This patch replaces lapic structure with kvm_vcpu in ioapic.c, making ioapic
independent of the local apic, as required by ia64.

Signed-off-by: Zhang Xiantao <xiantao.zhang@intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>