Fix more Coverity issues in the PHY lib

CID 369560 Missing unlock, in dft_fftw.c
CID 363710 Logically dead code, in resampler.c
CID 55097 Result is not floating point, in chest_test_dl.c
CID 351020 Result is not floating point, in chest_nbiot_test_dl.c

lib/src/phy/ch_estimation/test/chest_nbiot_test_dl.c

@@ -145,7 +145,7 @@ int main(int argc, char** argv)
     for (int n_port = 0; n_port < cell.base.nof_ports; n_port++) {
       srsran_vec_cf_zero(input, num_re);
       for (int i = 0; i < num_re; i++) {
-        input[i] = 0.5 - rand() / RAND_MAX + I * (0.5 - rand() / RAND_MAX);
+        input[i] = 0.5 - rand() / (float)RAND_MAX + I * (0.5 - rand() / (float)RAND_MAX);
       }
 
       srsran_vec_cf_zero(ce, num_re);

lib/src/phy/ch_estimation/test/chest_test_dl.c

@@ -137,7 +137,7 @@ int main(int argc, char** argv)
       for (uint32_t n_port = 0; n_port < cell.nof_ports; n_port++) {
         srsran_vec_cf_zero(input, num_re);
         for (i = 0; i < num_re; i++) {
-          input[i] = 0.5 - rand() / RAND_MAX + I * (0.5 - rand() / RAND_MAX);
+          input[i] = 0.5 - rand() / (float)RAND_MAX + I * (0.5 - rand() / (float)RAND_MAX);
         }
 
         srsran_vec_cf_zero(ce, num_re);

lib/src/phy/dft/dft_fftw.c

@@ -209,6 +209,7 @@ int srsran_dft_plan_guru_c(srsran_dft_plan_t* plan,
 
   plan->p = fftwf_plan_guru_dft(1, &iodim, 1, &howmany_dims, in_buffer, out_buffer, sign, FFTW_TYPE);
   if (!plan->p) {
+    pthread_mutex_unlock(&fft_mutex);
     return -1;
   }
   pthread_mutex_unlock(&fft_mutex);

lib/src/phy/resampling/resampler.c

@@ -234,7 +234,6 @@ static void resampler_fft_decimate(srsran_resampler_fft_t* q, const cf_t* input,
   while (count < nsamples) {
     uint32_t n = SRSRAN_MIN(q->window_sz, nsamples - count);
 
-    if (input) {
     // Copy input samples
     srsran_vec_cf_copy(q->in_buffer, &input[count], n);
 
@@ -255,9 +254,6 @@ static void resampler_fft_decimate(srsran_resampler_fft_t* q, const cf_t* input,
 
     // Execute iFFT
     srsran_dft_run_guru_c(&q->ifft);
-    } else {
-      srsran_vec_cf_zero(q->out_buffer, q->ifft.size);
-    }
 
     // Add previous state
     srsran_vec_sum_ccc(q->out_buffer, q->state, q->out_buffer, q->state_len);