KVM: nVMX: Copy processor-specific shadow-vmcs to VMCS12

Introduce a function used to copy fields from the processor-specific shadow
vmcs to the software controlled VMCS12

Signed-off-by: Abel Gordon <abelg@il.ibm.com>
Reviewed-by: Orit Wasserman <owasserm@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>