Makefile: Pass OF_SPL_REMOVE_PROPS to binman

Pass CONFIG_OF_SPL_REMOVE_PROPS to binman so that it can remove
properties correctly when producing FITs for SPL phases.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/Makefile b/Makefile
index 6738b86..ea562c2 100644
--- a/Makefile
+++ b/Makefile
@@ -1393,6 +1393,7 @@
 		-a tpl-dtb=$(CONFIG_TPL_OF_REAL) \
 		-a vpl-dtb=$(CONFIG_VPL_OF_REAL) \
 		-a pre-load-key-path=${PRE_LOAD_KEY_PATH} \
+		-a of-spl-remove-props=$(CONFIG_OF_SPL_REMOVE_PROPS) \
 		$(BINMAN_$(@F))
 
 OBJCOPYFLAGS_u-boot.ldr.hex := -I binary -O ihex