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/common/cmd_esbc_validate.c b/board/freescale/common/cmd_esbc_validate.c
index 3344653..7629d70 100644
--- a/board/freescale/common/cmd_esbc_validate.c
+++ b/board/freescale/common/cmd_esbc_validate.c
@@ -23,7 +23,7 @@
 	return 0;
 }
 
-#ifndef CONFIG_SPL_BUILD
+#ifndef CONFIG_XPL_BUILD
 static int do_esbc_validate(struct cmd_tbl *cmdtp, int flag, int argc,
 			    char *const argv[])
 {