Fixed a deadlock issue in the FPGA-based tracking loops

src/algorithms/tracking/gnuradio_blocks/dll_pll_veml_tracking_fpga.cc

@@ -1530,11 +1530,12 @@ int dll_pll_veml_tracking_fpga::general_work(int noutput_items __attribute__((un
                     {
                         boost::mutex::scoped_lock lock(d_mutex);
                         d_worker_is_done = false;
+                        l.unlock();
                         while (!d_worker_is_done)
                             {
                                 d_m_condition.wait(lock);
                             }
-
+                        l.lock();
                         // Signal alignment (skip samples until the incoming signal is aligned with local replica)
                         int64_t acq_trk_diff_samples;
                         double acq_trk_diff_seconds;