board: Use CONFIG_XPL_BUILD instead of CONFIG_SPL_BUILD

Use the new symbol to refer to any 'SPL' build, including TPL and VPL

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/nvidia/cardhu/Makefile b/board/nvidia/cardhu/Makefile
index 6f480cd..85d8829 100644
--- a/board/nvidia/cardhu/Makefile
+++ b/board/nvidia/cardhu/Makefile
@@ -3,6 +3,6 @@
 #  (C) Copyright 2010-2012
 #  NVIDIA Corporation <www.nvidia.com>
 
-obj-$(CONFIG_SPL_BUILD) += cardhu-spl.o
+obj-$(CONFIG_XPL_BUILD) += cardhu-spl.o
 
 obj-y	+= cardhu.o