KVM: x86 emulator: Use opcode::execute for BT family

BT : 0F A3
BTS: 0F AB
BTR: 0F B3
BTC: 0F BB

Group 8: 0F BA

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>