dm: Don't attach the device tree to SPL with of-platdata

When of-platdata is used in SPL we don't use the device tree. So there is no
point in attaching it. Adjust the Makefile to skip attaching the device tree
when of-platdata is enabled.

Signed-off-by: Simon Glass <sjg@chromium.org>

scripts/Makefile.spl

@@ -173,7 +173,7 @@ cmd_cat = cat $(filter-out $(PHONY), $^) > $@
 quiet_cmd_copy = COPY    $@
       cmd_copy = cp $< $@
 
-ifeq ($(CONFIG_SPL_OF_CONTROL)$(CONFIG_OF_SEPARATE),yy)
+ifeq ($(CONFIG_SPL_OF_CONTROL)$(CONFIG_OF_SEPARATE)$(CONFIG_SPL_OF_PLATDATA),yy)
 $(obj)/$(SPL_BIN)-dtb.bin: $(obj)/$(SPL_BIN)-nodtb.bin $(obj)/$(SPL_BIN)-pad.bin \
 		$(obj)/$(SPL_BIN).dtb FORCE
 	$(call if_changed,cat)