binman: Pass the toolpath to binman from the main Makefile

Pass in the toolpath in case binman needs to use tools compiled in the
U-Boot tools/ directory.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

Makefile

@@ -1213,6 +1213,7 @@ u-boot.ldr:	u-boot
 # Use 'make BINMAN_DEBUG=1' to enable debugging
 quiet_cmd_binman = BINMAN  $@
 cmd_binman = $(srctree)/tools/binman/binman $(if $(BINMAN_DEBUG),-D) \
+                --toolpath $(objtree)/tools \
                 build -u -d u-boot.dtb -O . -m \
 		-I . -I $(srctree) -I $(srctree)/board/$(BOARDDIR) \
 		$(BINMAN_$(@F))