i386: fix '-cpu ?' output for host cpu type

Since commit d6dcc558, '-cpu ?' shows the description of the
X86_CPU_TYPE_NAME("max") for the host CPU model:

Enables all features supported by the accelerator in the current host

instead of the expected:

KVM processor with all supported host features

or

HVF processor with all supported host features

This is caused by the early use of kvm_enabled() and hvf_enabled() in
a class_init function. Since the accelerator isn't configured yet, both
helpers return false unconditionally.

A QEMU binary will only be compiled with one of these accelerators, not
both. The appropriate description can thus be decided at build time.
Signed-off-by: NGreg Kurz <groug@kaod.org>
Message-Id: <153055056654.212317.4697363278304826913.stgit@bahia.lan>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

target/i386/cpu.c

@@ -2836,13 +2836,13 @@ static void host_x86_cpu_class_init(ObjectClass *oc, void *data)
     xcc->host_cpuid_required = true;
     xcc->ordering = 8;
 
-    if (kvm_enabled()) {
-        xcc->model_description =
-            "KVM processor with all supported host features ";
-    } else if (hvf_enabled()) {
-        xcc->model_description =
-            "HVF processor with all supported host features ";
-    }
+#if defined(CONFIG_KVM)
+    xcc->model_description =
+        "KVM processor with all supported host features ";
+#elif defined(CONFIG_HVF)
+    xcc->model_description =
+        "HVF processor with all supported host features ";
+#endif
 }
 
 static const TypeInfo host_x86_cpu_type_info = {