scripts: Makefile: Enable generation of symbols for DTBs

Enable generation of symbols for DTBs to allow merging of
device tree overlays.

Signed-off-by: Cristian Birsan <cristian.birsan@microchip.com>

Author: cristibirsan

scripts/Makefile.lib

@@ -308,7 +308,7 @@ $(obj)/%.dtb.S: $(obj)/%.dtb
 quiet_cmd_dtc = DTC     $@
 cmd_dtc = mkdir -p $(dir ${dtc-tmp}) ; \
 	$(CPP) $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ; \
-	$(DTC) -O dtb -o $@ -b 0 \
+	$(DTC) -@ -O dtb -o $@ -b 0 \
 		$(addprefix -i,$(dir $<) $(DTC_INCLUDE)) $(DTC_FLAGS) \
 		-d $(depfile).dtc.tmp $(dtc-tmp) ; \
 	cat $(depfile).pre.tmp $(depfile).dtc.tmp > $(depfile)