KVM: x86 emulator: rearrange fastop definitions

Make fastop opcodes usable in other emulations.

Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi.kivity@gmail.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>