i386/tdx: Handle KVM_SYSTEM_EVENT_TDX_FATAL

i386/tdx: Handle KVM_SYSTEM_EVENT_TDX_FATAL

TD guest can use TDG.VP.VMCALL<REPORT_FATAL_ERROR> to request
termination. KVM translates such request into KVM_EXIT_SYSTEM_EVENT with
type of KVM_SYSTEM_EVENT_TDX_FATAL.

Add hanlder for such exit. Parse and print the error message, and
terminate the TD guest in the handler.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250508150002.689633-29-xiaoyao.li@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>