x86/acrn: Use HYPERVISOR_CALLBACK_VECTOR for ACRN guest upcall vector

Use the HYPERVISOR_CALLBACK_VECTOR to notify an ACRN guest.

Co-developed-by: Jason Chen CJ <jason.cj.chen@intel.com>
Signed-off-by: Jason Chen CJ <jason.cj.chen@intel.com>
Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/1559108037-18813-4-git-send-email-yakui.zhao@intel.com