The vmcs12 fields offsets are constant and known at compile time.  Store
the associated offset for each shadowed field to avoid the costly lookup
in vmcs_field_to_offset() when copying between vmcs12 and the shadow
VMCS.  Avoiding the costly lookup reduces the latency of copying by
~100 cycles in each direction.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>