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/liebherr/display5/Makefile b/board/liebherr/display5/Makefile
index ee503ad..c62583a 100644
--- a/board/liebherr/display5/Makefile
+++ b/board/liebherr/display5/Makefile
@@ -4,7 +4,7 @@
 #
 # SPDX-License-Identifier:    GPL-2.0+
 #
-ifdef CONFIG_SPL_BUILD
+ifdef CONFIG_XPL_BUILD
 obj-y = spl.o
 else
 obj-y := display5.o