target-i386: fix typo

The impact is small because kvm_get_vcpu_events fixes env->hflags, but
it is wrong and could cause INITs to be delayed arbitrarily with
-machine kernel_irqchip=off.
Reported-by: NAchille Fouilleul <achille.fouilleul@gadz.org>
Reviewed-by: NRichard Henderson <rth@twiddle.net>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

target-i386/kvm.c

@@ -2855,7 +2855,7 @@ MemTxAttrs kvm_arch_post_run(CPUState *cpu, struct kvm_run *run)
     if (run->flags & KVM_RUN_X86_SMM) {
         env->hflags |= HF_SMM_MASK;
     } else {
-        env->hflags &= HF_SMM_MASK;
+        env->hflags &= ~HF_SMM_MASK;
     }
     if (run->if_flag) {
         env->eflags |= IF_MASK;