mustek_pp: Handle status argument correctly in pa4s2_init()

Currently the pointer itself is overwritten, when it is intended that
the pointer be derefenced first.

sanei/sanei_pa4s2.c

@@ -270,7 +270,7 @@ pa4s2_init (SANE_Status *status)
   if (first_time == SANE_FALSE)
     {
       DBG (5, "pa4s2_init: sanei already initialized\n");
-      status = SANE_STATUS_GOOD;
+      *status = SANE_STATUS_GOOD;
       return 0;
     }