apic: Inject external NMI events via LINT1

apic: Inject external NMI events via LINT1

On real hardware, NMI button events are injected via the LINT1 line of
the APICs. E.g. kdump expect this wiring and gets upset if the per-APIC
LINT1 mask is not respected, i.e. if NMIs are injected to VCPUs that
should not receive them. Change the APIC emulation code to reflect this.

Based on qemu-kvm patch by Lai Jiangshan.

CC: Lai Jiangshan <laijs@cn.fujitsu.com>
Reported-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>