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/udoo/udoo_spl.c b/board/udoo/udoo_spl.c
index 6c47753..b845284 100644
--- a/board/udoo/udoo_spl.c
+++ b/board/udoo/udoo_spl.c
@@ -23,7 +23,7 @@
 #include <asm/arch/sys_proto.h>
 #include <spl.h>
 
-#if defined(CONFIG_SPL_BUILD)
+#if defined(CONFIG_XPL_BUILD)
 #include <asm/arch/mx6-ddr.h>
 
 /*