KVM: nVMX: Rename prepare_vmcs02_*_full to prepare_vmcs02_*_rare

These function do not prepare the entire state of the vmcs02, only the
rarely needed parts.  Rename them to make this clearer.

Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>