hv: initial host reset implementation

- add the GUEST_FLAG_HIGHEST_SEVERITY flag to indicate that the guest has
  privilege to reboot the host system.

- this flag is statically assigned to guest(s) in vm_configurations.c in
  different scenarios.

- implement reset_host() function to reset the host. First try the ACPI
  reset register if available, then try the 0xcf9 PIO.

Tracked-On: #3145
Signed-off-by: Sainath Grandhi <sainath.grandhi@intel.com>
Signed-off-by: Zide Chen <zide.chen@intel.com>
Acked-by: Anthony Xu <anthony.xu@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

hypervisor/include/arch/x86/guest/vm.h

@@ -218,6 +218,7 @@ void vrtc_init(struct acrn_vm *vm);
 
 bool is_lapic_pt_configured(const struct acrn_vm *vm);
 bool is_rt_vm(const struct acrn_vm *vm);
+bool is_highest_severity_vm(const struct acrn_vm *vm);
 bool vm_hide_mtrr(const struct acrn_vm *vm);
 
 #endif /* !ASSEMBLER */