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/lib/zimage.c b/arch/arm/lib/zimage.c
index 5128725..7e1cd4d 100644
--- a/arch/arm/lib/zimage.c
+++ b/arch/arm/lib/zimage.c
@@ -24,14 +24,14 @@
 
 	if (zi->zi_magic != LINUX_ARM_ZIMAGE_MAGIC &&
 	    zi->zi_magic != BAREBOX_IMAGE_MAGIC) {
-		if (!IS_ENABLED(CONFIG_SPL_BUILD))
+		if (!IS_ENABLED(CONFIG_XPL_BUILD))
 			puts("zimage: Bad magic!\n");
 		return 1;
 	}
 
 	*start = zi->zi_start;
 	*end = zi->zi_end;
-	if (!IS_ENABLED(CONFIG_SPL_BUILD))
+	if (!IS_ENABLED(CONFIG_XPL_BUILD))
 		printf("Kernel image @ %#08lx [ %#08lx - %#08lx ]\n",
 		       image, *start, *end);