Fixed USRP capture sync due to missing channel ptr

lib/examples/usrp_capture_sync.c

@@ -100,7 +100,11 @@ void parse_args(int argc, char **argv) {
 
 int srslte_rf_recv_wrapper(void *h, cf_t *data[SRSLTE_MAX_PORTS], uint32_t nsamples, srslte_timestamp_t *t) {
   DEBUG(" ----  Receive %d samples  ---- \n", nsamples);
-  return srslte_rf_recv_with_time_multi(h, (void**)data[0], nsamples, true, NULL, NULL);
+  void* ptr[SRSLTE_MAX_PORTS];
+  for (int i = 0; i < SRSLTE_MAX_PORTS; i++) {
+    ptr[i] = data[i];
+  }
+  return srslte_rf_recv_with_time_multi(h, ptr, nsamples, true, NULL, NULL);
 }
 
 int main(int argc, char **argv) {