acpi: fix pvpanic device is not shown in ui

Commit 2332333 added a _STA method that hides the device. The fact
that the device is not shown in the gui make it harder to install its
Windows' device.

https://bugzilla.redhat.com/show_bug.cgi?id=1238141

Signed-off-by: Gal Hammer <ghammer@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>

hw/i386/acpi-build.c

@@ -1108,8 +1108,8 @@ build_ssdt(GArray *table_data, GArray *linker,
         aml_append(field, aml_named_field("PEPT", 8));
         aml_append(dev, field);
 
-        /* device present, functioning, decoding, not shown in UI */
-        aml_append(dev, aml_name_decl("_STA", aml_int(0xB)));
+        /* device present, functioning, decoding, shown in UI */
+        aml_append(dev, aml_name_decl("_STA", aml_int(0xF)));
 
         method = aml_method("RDPT", 0);
         aml_append(method, aml_store(aml_name("PEPT"), aml_local(0)));