bootstage: Convert progress numbers 1-9 into enums

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/common/image.c b/common/image.c
index 8df03f5..1359246 100644
--- a/common/image.c
+++ b/common/image.c
@@ -895,7 +895,7 @@
 			printf("## Loading init Ramdisk from Legacy "
 					"Image at %08lx ...\n", rd_addr);
 
-			show_boot_progress(9);
+			show_boot_progress(BOOTSTAGE_ID_LOAD_RAMDISK);
 			rd_hdr = image_get_ramdisk(rd_addr, arch,
 							images->verify);