According to Intel SDM 26.2.1.1, the following rules should be enforced
on vmentry:

 *  If the "NMI exiting" VM-execution control is 0, "Virtual NMIs"
    VM-execution control must be 0.
 *  If the “virtual NMIs” VM-execution control is 0, the “NMI-window
    exiting” VM-execution control must be 0.

This patch enforces these rules when entering an L2 guest.
Signed-off-by: NKrish Sadhukhan <krish.sadhukhan@oracle.com>
Reviewed-by: NLiran Alon <liran.alon@oracle.com>
Reviewed-by: NJim Mattson <jmattson@google.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>