include: 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/include/fdtdec.h b/include/fdtdec.h
index e80de24..555c952 100644
--- a/include/fdtdec.h
+++ b/include/fdtdec.h
@@ -143,7 +143,7 @@
 static inline u8 *dtb_dt_embedded(void)
 {
 #ifdef CONFIG_OF_EMBED
-# ifdef CONFIG_SPL_BUILD
+# ifdef CONFIG_XPL_BUILD
 	return __dtb_dt_spl_begin;
 # else
 	return __dtb_dt_begin;