KVM: x86 emulator: avoid calling wbinvd() macro

Commit 0b56652e33c72092956c651ab6ceb9f0ad081153 fails to build:

  CC [M]  arch/x86/kvm/emulate.o
arch/x86/kvm/emulate.c: In function 'x86_emulate_insn':
arch/x86/kvm/emulate.c:4095:25: error: macro "wbinvd" passed 1 arguments, but takes just 0
arch/x86/kvm/emulate.c:4095:3: warning: statement with no effect
make[2]: *** [arch/x86/kvm/emulate.o] Error 1
make[1]: *** [arch/x86/kvm] Error 2
make: *** [arch/x86] Error 2

Work around this for now.

Signed-off-by: Clemens Noss <cnoss@gmx.de>
Signed-off-by: Avi Kivity <avi@redhat.com>