KVM: nVMX: call kvm_skip_emulated_instruction in nested_vmx_{fail,succeed}

... as every invocation of nested_vmx_{fail,succeed} is immediately
followed by a call to kvm_skip_emulated_instruction().  This saves
a bit of code and eliminates some silly paths, e.g. nested_vmx_run()
ended up with a goto label purely used to call and return
kvm_skip_emulated_instruction().
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>