lib: Fix build condition for tiny-printf

This should be checking for any SPL build. Drop the use of SPL_TPL_ since
it is not necessary and will not work with split config.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/Makefile b/lib/Makefile
index a282e40..10aa7ac 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -127,7 +127,7 @@
 obj-$(CONFIG_LIB_RAND) += rand.o
 obj-y += panic.o
 
-ifeq ($(CONFIG_$(SPL_TPL_)BUILD),y)
+ifeq ($(CONFIG_SPL_BUILD),y)
 # SPL U-Boot may use full-printf, tiny-printf or none at all
 ifdef CONFIG_$(SPL_TPL_)USE_TINY_PRINTF
 obj-$(CONFIG_$(SPL_TPL_)SPRINTF) += tiny-printf.o