Fix "Comparison is always true because ret >= 0" LGTM warnings

... and refactor out some other dead code in the vacinity of these warnings

lib/src/phy/ue/ue_cell_search.c

@@ -265,7 +265,7 @@ int srslte_ue_cellsearch_scan(srslte_ue_cellsearch_t*       q,
   float    max_peak_value     = -1.0;
   uint32_t nof_detected_cells = 0;
 
-  for (uint32_t N_id_2 = 0; N_id_2 < 3 && ret >= 0; N_id_2++) {
+  for (uint32_t N_id_2 = 0; N_id_2 < 3; N_id_2++) {
     INFO("CELL SEARCH: Starting scan for N_id_2=%d\n", N_id_2);
     ret = srslte_ue_cellsearch_scan_N_id_2(q, N_id_2, &found_cells[N_id_2]);
     if (ret < 0) {

lib/src/phy/ue/ue_mib.c

@@ -245,17 +245,21 @@ int srslte_ue_mib_sync_decode(srslte_ue_mib_sync_t* q,
   uint32_t nof_frames = 0;
   int      mib_ret    = SRSLTE_UE_MIB_NOTFOUND;
 
-  if (q != NULL) {
+  if (q == NULL) {
+    return ret;
+  }
+
   srslte_ue_mib_sync_reset(q);
 
-    ret = SRSLTE_SUCCESS;
   do {
     mib_ret = SRSLTE_UE_MIB_NOTFOUND;
     ret     = srslte_ue_sync_zerocopy(&q->ue_sync, q->sf_buffer, MIB_BUFFER_MAX_SAMPLES);
     if (ret < 0) {
       ERROR("Error calling srslte_ue_sync_work()\n");
       return -1;
-      } else if (srslte_ue_sync_get_sfidx(&q->ue_sync) == 0) {
+    }
+
+    if (srslte_ue_sync_get_sfidx(&q->ue_sync) == 0) {
       if (ret == 1) {
         mib_ret = srslte_ue_mib_decode(&q->ue_mib, bch_payload, nof_tx_ports, sfn_offset);
       } else {
@@ -264,10 +268,7 @@ int srslte_ue_mib_sync_decode(srslte_ue_mib_sync_t* q,
       }
       nof_frames++;
     }
-    } while (mib_ret == SRSLTE_UE_MIB_NOTFOUND && ret >= 0 && nof_frames < max_frames_timeout);
-    if (mib_ret < 0) {
-      ret = mib_ret;
-    }
-  }
+  } while (mib_ret == SRSLTE_UE_MIB_NOTFOUND && nof_frames < max_frames_timeout);
+
   return mib_ret;
 }

lib/src/phy/ue/ue_mib_nbiot.c

@@ -244,18 +244,23 @@ int srslte_ue_mib_sync_nbiot_decode(srslte_ue_mib_sync_nbiot_t* q,
                                     uint32_t*                   nof_tx_ports,
                                     int*                        sfn_offset)
 {
+  int      ret        = SRSLTE_ERROR_INVALID_INPUTS;
+  uint32_t nof_frames = 0;
   int      mib_ret    = SRSLTE_UE_MIB_NBIOT_NOTFOUND;
 
-  if (q != NULL) {
-    int      ret        = SRSLTE_SUCCESS;
-    uint32_t nof_frames = 0;
+  if (q == NULL) {
+      return ret;
+  }
+
   do {
     mib_ret = SRSLTE_UE_MIB_NBIOT_NOTFOUND;
     ret     = srslte_ue_sync_nbiot_zerocopy_multi(&q->ue_sync, q->sf_buffer);
     if (ret < 0) {
       fprintf(stderr, "Error calling srslte_ue_sync_nbiot_zerocopy_multi()\n");
       break;
-      } else if (srslte_ue_sync_nbiot_get_sfidx(&q->ue_sync) == 0) {
+    }
+
+    if (srslte_ue_sync_nbiot_get_sfidx(&q->ue_sync) == 0) {
       mib_ret = srslte_ue_mib_nbiot_decode(&q->ue_mib, NULL, bch_payload, nof_tx_ports, sfn_offset);
       if (mib_ret < 0) {
         DEBUG("Resetting NPBCH decoder after %d frames\n", q->ue_mib.frame_cnt);
@@ -263,10 +268,7 @@ int srslte_ue_mib_sync_nbiot_decode(srslte_ue_mib_sync_nbiot_t* q,
       }
       nof_frames++;
     }
-    } while (mib_ret == SRSLTE_UE_MIB_NBIOT_NOTFOUND && ret >= 0 && nof_frames < max_frames_timeout);
-    if (mib_ret < 0) {
-      ret = mib_ret;
-    }
-  }
+  } while (mib_ret == SRSLTE_UE_MIB_NBIOT_NOTFOUND && nof_frames < max_frames_timeout);
+
   return mib_ret;
 }