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/ls1043aqds/Makefile b/board/freescale/ls1043aqds/Makefile
index 49d8d7d..ff83078 100644
--- a/board/freescale/ls1043aqds/Makefile
+++ b/board/freescale/ls1043aqds/Makefile
@@ -5,7 +5,7 @@
 #
 
 obj-y += ddr.o
-ifndef CONFIG_SPL_BUILD
+ifndef CONFIG_XPL_BUILD
 obj-y += eth.o
 endif
 obj-y += ls1043aqds.o