Makefile: Pass the U-Boot phase to dtoc

Pass the U-Boot phase as a parameter so dtoc can use it. At present it is
ether "spl" or "tpl".

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/scripts/Makefile.spl b/scripts/Makefile.spl
index 1fd63ef..bfae9a4 100644
--- a/scripts/Makefile.spl
+++ b/scripts/Makefile.spl
@@ -311,7 +311,7 @@
 pythonpath = PYTHONPATH=scripts/dtc/pylibfdt
 
 DTOC_ARGS := $(pythonpath) $(srctree)/tools/dtoc/dtoc \
-	-d $(obj)/$(SPL_BIN).dtb
+	-d $(obj)/$(SPL_BIN).dtb -p $(SPL_NAME)
 
 quiet_cmd_dtoc = DTOC    $@
 cmd_dtoc = $(DTOC_ARGS) -c $(obj)/dts -C include/generated all