[fdt] Make DTBs generated by make_dtb.sh overlay-ready

Generate symbols node when compiling dts files so they can be modified
during boot-time by applying overlays.

sys/tools/fdt/make_dtb.sh

@@ -20,5 +20,5 @@ for d in ${dts}; do
     dtb=${dtb_path}/`basename $d .dts`.dtb
     echo "converting $d -> $dtb"
     cpp -P -x assembler-with-cpp -I $S/gnu/dts/include -I $S/boot/fdt/dts/${MACHINE} -I $S/gnu/dts/${MACHINE} -include $d /dev/null | 
-	dtc -O dtb -o $dtb -b 0 -p 1024 -i $S/boot/fdt/dts/${MACHINE} -i $S/gnu/dts/${MACHINE}
+	dtc -@ -O dtb -o $dtb -b 0 -p 1024 -i $S/boot/fdt/dts/${MACHINE} -i $S/gnu/dts/${MACHINE}
 done