fdt: Update Makefile rules with the new OF_REAL Kconfig

Simplify some of the Makefile rules using this Kconfig.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/Makefile b/Makefile
index a09f48f..5ad06b8 100644
--- a/Makefile
+++ b/Makefile
@@ -1292,10 +1292,6 @@
 # Use 'make BINMAN_VERBOSE=3' to set vebosity level
 default_dt := $(if $(DEVICE_TREE),$(DEVICE_TREE),$(CONFIG_DEFAULT_DEVICE_TREE))
 
-# Tell binman whether we have a devicetree for SPL and TPL
-have_spl_dt := $(if $(CONFIG_SPL_OF_PLATDATA),,$(CONFIG_SPL_OF_CONTROL))
-have_tpl_dt := $(if $(CONFIG_TPL_OF_PLATDATA),,$(CONFIG_TPL_OF_CONTROL))
-
 quiet_cmd_binman = BINMAN  $@
 cmd_binman = $(srctree)/tools/binman/binman $(if $(BINMAN_DEBUG),-D) \
                 --toolpath $(objtree)/tools \
@@ -1309,7 +1305,8 @@
 		-a scp-path=$(SCP) \
 		-a spl-bss-pad=$(if $(CONFIG_SPL_SEPARATE_BSS),,1) \
 		-a tpl-bss-pad=$(if $(CONFIG_TPL_SEPARATE_BSS),,1) \
-		-a spl-dtb=$(have_spl_dt) -a tpl-dtb=$(have_tpl_dt) \
+		-a spl-dtb=$(CONFIG_SPL_OF_REAL) \
+		-a tpl-dtb=$(CONFIG_SPL_OF_REAL) \
 		$(BINMAN_$(@F))
 
 OBJCOPYFLAGS_u-boot.ldr.hex := -I binary -O ihex