sw64: kvm: optimize external interrupts assignment for guest

Sunway inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I56WV8



--------------------------------

Target cpu for all external interrupts of guest os was assigned by
hypervisor. However, it's not a common solution and it will cause
system crash in cpu hotplug.

This patch optimizes the assignment policy. Target cpu and target
vector for MSI of guest are assigned by itself. Target cpu of other
external interrupts is bound to vCPU0 by hypervisor.

Signed-off-by: Zhang Yi <zhangyi@wxiat.com>
Reviewed-by: He Sheng <hesheng@wxiat.com>
Signed-off-by: Gu Zitao <guzitao@wxiat.com>