global: Use CONFIG_XPL_BUILD instead of CONFIG_SPL_BUILD

Complete this rename for all directories outside arch/ board/ drivers/
and include/

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/boot/image-fit-sig.c b/boot/image-fit-sig.c
index fe328df..35873b1 100644
--- a/boot/image-fit-sig.c
+++ b/boot/image-fit-sig.c
@@ -48,7 +48,7 @@
 	 * Use malloc() except in SPL (to save code size). In SPL the caller
 	 * must allocate the array.
 	 */
-	if (!IS_ENABLED(CONFIG_SPL_BUILD) && !region)
+	if (!IS_ENABLED(CONFIG_XPL_BUILD) && !region)
 		region = calloc(sizeof(*region), count);
 	if (!region)
 		return NULL;