If /dev/hwrng exists then set the hrng type accordingly

src/freedombone

       return
   fi
 
+  # if the hrng type has not been set but /dev/hwrng is detected
+  if [[ $HWRNG_TYPE != "beaglebone" ]]; then
+      if [ -e /dev/hwrng ]; then
+          HWRNG_TYPE="beaglebone"
+      fi
+  fi
+
   case $HWRNG_TYPE in
     beaglebone)
     apt-get -y install rng-tools