Use LOG_A for log messages intended for analysis

This change allows us to disable the LOG_I messages to reduce
overhead.

Removed LOG_VAR macro because it was used in only one place, and
a better solution is to simply use `__attribute__((unused))`.

targets/RT/USER/lte-ru.c

@@ -1544,6 +1544,7 @@ static void *ru_stats_thread(void *param) {
 static void *ru_thread_tx( void *param ) {
   RU_t *ru         = (RU_t *)param;
   RU_proc_t *proc  = &ru->proc;
+  __attribute__((unused))
   LTE_DL_FRAME_PARMS *fp = ru->frame_parms;
   PHY_VARS_eNB *eNB;
   L1_proc_t *eNB_proc;
@@ -1958,6 +1959,7 @@ static void *ru_thread( void *param ) {
 // This thread run the initial synchronization like a UE
 void *ru_thread_synch(void *arg) {
   RU_t *ru = (RU_t *)arg;
+  __attribute__((unused))
   LTE_DL_FRAME_PARMS *fp = ru->frame_parms;
   int64_t peak_val, avg;
   static int ru_thread_synch_status = 0;