x86/acrn: Introduce acrn_{setup, remove}_intr_handler()

x86/acrn: Introduce acrn_{setup, remove}_intr_handler()

The ACRN Hypervisor builds an I/O request when a trapped I/O access
happens in User VM. Then, ACRN Hypervisor issues an upcall by sending
a notification interrupt to the Service VM. HSM in the Service VM needs
to hook the notification interrupt to handle I/O requests.

Notification interrupts from ACRN Hypervisor are already supported and
a, currently uninitialized, callback called.

Export two APIs for HSM to setup/remove its callback.

Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Fengwei Yin <fengwei.yin@intel.com>
Cc: Zhi Wang <zhi.a.wang@intel.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Yu Wang <yu1.wang@intel.com>
Cc: Reinette Chatre <reinette.chatre@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Originally-by: Yakui Zhao <yakui.zhao@intel.com>
Reviewed-by: Zhi Wang <zhi.a.wang@intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Acked-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Shuo Liu <shuo.a.liu@intel.com>
Link: https://lore.kernel.org/r/20210207031040.49576-3-shuo.a.liu@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>