target-unicore32: Catch attempt to instantiate abstract type in cpu_init()

Fixes -cpu unicore32-cpu asserting.

Cc: qemu-stable@nongnu.org
Signed-off-by: NAndreas Färber <afaerber@suse.de>

target-unicore32/cpu.c

@@ -31,7 +31,8 @@ static ObjectClass *uc32_cpu_class_by_name(const char *cpu_model)
     }
 
     oc = object_class_by_name(cpu_model);
-    if (oc != NULL && !object_class_dynamic_cast(oc, TYPE_UNICORE32_CPU)) {
+    if (oc != NULL && (!object_class_dynamic_cast(oc, TYPE_UNICORE32_CPU) ||
+                       object_class_is_abstract(oc))) {
         oc = NULL;
     }
     return oc;