to deal with the cpu 100% issue of pre_scd_task thread

(cherry picked from commit d528bb824d4515a61acaaf2eb35c0c659fc3a6db)

targets/RT/USER/lte-ru.c

@@ -2138,6 +2138,7 @@ void *pre_scd_task( void *param ) {
     }
 
     if(old_subframe == eNB->subframe){
+      usleep(100);
       continue;
     }