Move CALLBACK into the 'init' section,

to have it called once only.

src/xspice/icm/digital/d_osc/cfunc.mod

@@ -71,11 +71,12 @@ void cm_d_osc(ARGS)
     double        ctl, period, delta, when;
     int           csize, i;
 
-    CALLBACK = cm_d_osc_callback;
-
     csize = PARAM_SIZE(cntl_array);
+
     if (INIT) {
 
+        CALLBACK = cm_d_osc_callback;
+
         /* Validate PWL table. */
 
         for (i = 0; i < csize - 1; ++i) {