KVM: x86 emulator: add new ->halt() callback

Instead of reaching into vcpu internals.

Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 5d774e9..210df51 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3913,7 +3913,7 @@
 		c->dst.type = OP_NONE;	/* Disable writeback. */
 		break;
 	case 0xf4:              /* hlt */
-		ctxt->vcpu->arch.halt_request = 1;
+		ctxt->ops->halt(ctxt);
 		break;
 	case 0xf5:	/* cmc */
 		/* complement carry flag from eflags reg */