arch: 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/arch/arm/cpu/armv8/fsl-layerscape/spl.c b/arch/arm/cpu/armv8/fsl-layerscape/spl.c
index a739ff2..1f1e3d4 100644
--- a/arch/arm/cpu/armv8/fsl-layerscape/spl.c
+++ b/arch/arm/cpu/armv8/fsl-layerscape/spl.c
@@ -41,7 +41,7 @@
 	return 0;
 }
 
-#ifdef CONFIG_SPL_BUILD
+#ifdef CONFIG_XPL_BUILD
 
 void spl_board_init(void)
 {
@@ -136,4 +136,4 @@
 	return 1;
 }
 #endif	/* CONFIG_SPL_OS_BOOT */
-#endif /* CONFIG_SPL_BUILD */
+#endif /* CONFIG_XPL_BUILD */