pc: add SMM property

The property can take values on, off or auto.  The default is "off"
for KVM and pre-2.4 machines, otherwise "auto" (which makes it
available on TCG or on new-enough kernels).

Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/target-i386/kvm_i386.h b/target-i386/kvm_i386.h
index cac30fd..e557e94 100644
--- a/target-i386/kvm_i386.h
+++ b/target-i386/kvm_i386.h
@@ -14,6 +14,7 @@
 #include "sysemu/kvm.h"
 
 bool kvm_allows_irq0_override(void);
+bool kvm_has_smm(void);
 void kvm_arch_reset_vcpu(X86CPU *cs);
 void kvm_arch_do_init_vcpu(X86CPU *cs);