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/freescale/ls1021aqds/ls1021aqds.c b/board/freescale/ls1021aqds/ls1021aqds.c
index 930ef6be..0bdd468 100644
--- a/board/freescale/ls1021aqds/ls1021aqds.c
+++ b/board/freescale/ls1021aqds/ls1021aqds.c
@@ -181,7 +181,7 @@
 	return 0;
 }
 
-#ifdef CONFIG_SPL_BUILD
+#ifdef CONFIG_XPL_BUILD
 void board_init_f(ulong dummy)
 {
 #ifdef CONFIG_NAND_BOOT