binman: Rename TYPE_STAGE to TYPE_LEGACY_STAGE

In preparation for changing how stages are stored, rename the existing
stage tag.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/cbfs.h b/include/cbfs.h
index 38efb1d..2bc5de2 100644
--- a/include/cbfs.h
+++ b/include/cbfs.h
@@ -22,7 +22,7 @@
 enum cbfs_filetype {
 	CBFS_TYPE_BOOTBLOCK = 0x01,
 	CBFS_TYPE_CBFSHEADER = 0x02,
-	CBFS_TYPE_STAGE = 0x10,
+	CBFS_TYPE_LEGACY_STAGE = 0x10,
 	CBFS_TYPE_PAYLOAD = 0x20,
 	CBFS_TYPE_SELF = CBFS_TYPE_PAYLOAD,