fix ref type name

Author: myk002

df.units.xml

@@ -2825,7 +2825,7 @@
         </static-array>
         <int32_t name='spotted_num'/>
         <pointer type-name='activity_event_conflictst' name='conflict_name'/>
-        <int32_t name='alarm_activity_id' ref-target='activity'/>
+        <int32_t name='alarm_activity_id' ref-target='activity_entry'/>
         <int32_t name='alarm_unit_id' ref-target='unit'/>
     </struct-type>