[Makefile] Add padding to binary files for the device

build/targets.device.mak

@@ -9,6 +9,11 @@ products += $(patsubst %.$(EXE),%.map,$(filter %.$(EXE),$(products)))
 %.bin: %.$(EXE)
 	@echo "OBJCOPY $@"
 	$(Q) $(OBJCOPY) -O binary $< $@
+# We pad the device binary files because there was a bug in an older version of
+# the dfu code, and it did not upload properly a binary of length non-multiple
+# of 32 bits.
+	@echo "Padding $@"
+	@echo "\x1\x1\x1\x1" >> $@
 
 .PHONY: %_size
 %_size: %.$(EXE)