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/conclusive/kstr-sama5d27/kstr-sama5d27.c b/board/conclusive/kstr-sama5d27/kstr-sama5d27.c
index 64282ae..58582bc 100644
--- a/board/conclusive/kstr-sama5d27/kstr-sama5d27.c
+++ b/board/conclusive/kstr-sama5d27/kstr-sama5d27.c
@@ -141,7 +141,7 @@
 }
 
 /* SPL */
-#ifdef CONFIG_SPL_BUILD
+#ifdef CONFIG_XPL_BUILD
 void spl_board_init(void)
 {
 }