Makefile: Tidy up the TPL build rules

These should follow the same pattern as SPL, for consistency. Fix them.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/Makefile b/Makefile
index 9f220de..82c35a9 100644
--- a/Makefile
+++ b/Makefile
@@ -2110,10 +2110,13 @@
 spl/boot.bin: spl/u-boot-spl
 	@:
 
-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/u-boot-tpl.bin: tpl/u-boot-tpl
+	@:
 	$(TPL_SIZE_CHECK)
 
+tpl/u-boot-tpl: tools prepare $(if $(CONFIG_TPL_OF_CONTROL),dts/dt.dtb)
+	$(Q)$(MAKE) obj=tpl -f $(srctree)/scripts/Makefile.spl all
+
 TAG_SUBDIRS := $(patsubst %,$(srctree)/%,$(u-boot-dirs) include)
 
 FIND := find