Fix - Issue with uninitialized structure in ULSIM

- Changed malloc to calloc to set all values to zero to remove the
  valgrind issue with uninitialized structure values in RC.gNB structure

openair1/SIMULATION/NR_PHY/ulsim.c

@@ -494,7 +494,7 @@ int main(int argc, char **argv)
   UE2gNB->max_Doppler = maxDoppler;
 
   RC.gNB = (PHY_VARS_gNB **) malloc(sizeof(PHY_VARS_gNB *));
-  RC.gNB[0] = malloc(sizeof(PHY_VARS_gNB));
+  RC.gNB[0] = calloc(1,sizeof(PHY_VARS_gNB));
   gNB = RC.gNB[0];
   //gNB_config = &gNB->gNB_config;