pc: Fix typo on PC_COMPAT_2_12

I forgot a hyphen when amending the compat code on commit
e0051647 ("i386: Enable TOPOEXT feature on AMD EPYC CPU").

Fixes: e0051647Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>
Message-Id: <20180703011026.18650-1-ehabkost@redhat.com>
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>

include/hw/i386/pc.h

@@ -309,7 +309,7 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);
         .property = "xlevel",\
         .value    = stringify(0x8000000a),\
     },{\
-        .driver   = "EPYC-IBPB" TYPE_X86_CPU,\
+        .driver   = "EPYC-IBPB-" TYPE_X86_CPU,\
         .property = "xlevel",\
         .value    = stringify(0x8000000a),\
     },