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/ti/ks2_evm/board_k2hk.c b/board/ti/ks2_evm/board_k2hk.c
index 2b5d2d7..93249fa 100644
--- a/board/ti/ks2_evm/board_k2hk.c
+++ b/board/ti/ks2_evm/board_k2hk.c
@@ -116,7 +116,7 @@
 }
 #endif
 
-#ifdef CONFIG_SPL_BUILD
+#ifdef CONFIG_XPL_BUILD
 void spl_init_keystone_plls(void)
 {
 	init_plls();