arch: 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/arch/arm/mach-imx/mx6/litesom.c b/arch/arm/mach-imx/mx6/litesom.c
index 03e1214..c6bf933 100644
--- a/arch/arm/mach-imx/mx6/litesom.c
+++ b/arch/arm/mach-imx/mx6/litesom.c
@@ -78,7 +78,7 @@
 }
 #endif
 
-#ifdef CONFIG_SPL_BUILD
+#ifdef CONFIG_XPL_BUILD
 #include <linux/libfdt.h>
 #include <spl.h>
 #include <asm/arch/mx6-ddr.h>