Makefile: Simplify devicetree rules for SPL/TPL

The current logic checks several options to decide whether SPL/TPL need
the U-Boot devicetree to be built. In fact we can check OF_CONTROL, which
is enabled in all cases that matter.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/Makefile b/Makefile
index 3f28333..9f220de 100644
--- a/Makefile
+++ b/Makefile
@@ -2095,9 +2095,7 @@
 spl/u-boot-spl-dtb.hex: spl/u-boot-spl
 	@:
 
-spl/u-boot-spl: tools prepare \
-		$(if $(CONFIG_OF_SEPARATE)$(CONFIG_OF_EMBED)$(CONFIG_SPL_OF_PLATDATA),dts/dt.dtb) \
-		$(if $(CONFIG_OF_SEPARATE)$(CONFIG_OF_EMBED)$(CONFIG_TPL_OF_PLATDATA),dts/dt.dtb)
+spl/u-boot-spl: tools prepare $(if $(CONFIG_SPL_OF_CONTROL),dts/dt.dtb)
 	$(Q)$(MAKE) obj=spl -f $(srctree)/scripts/Makefile.spl all
 
 spl/sunxi-spl.bin: spl/u-boot-spl
@@ -2112,8 +2110,7 @@
 spl/boot.bin: spl/u-boot-spl
 	@:
 
-tpl/u-boot-tpl.bin: tools prepare \
-		$(if $(CONFIG_OF_SEPARATE)$(CONFIG_OF_EMBED)$(CONFIG_SPL_OF_PLATDATA),dts/dt.dtb)
+tpl/u-boot-tpl.bin: tools prepare $(if $(CONFIG_TPL_OF_CONTROL),dts/dt.dtb)
 	$(Q)$(MAKE) obj=tpl -f $(srctree)/scripts/Makefile.spl all
 	$(TPL_SIZE_CHECK)