app: aboot: check minimum size of ubi image.

Check minimum size of ubi image.

Change-Id: Ia392698071874fd043066a5d02daf7083a0cb977
diff --git a/app/aboot/aboot.c b/app/aboot/aboot.c
index c7e65cb..6afebe5 100755
--- a/app/aboot/aboot.c
+++ b/app/aboot/aboot.c
@@ -3482,7 +3482,8 @@
 	}
 
 	dprintf(INFO, "writing %d bytes to '%s'\n", sz, ptn->name);
-	if ((sz > UBI_MAGIC_SIZE) && (!memcmp((void *)data, UBI_MAGIC, UBI_MAGIC_SIZE))) {
+	if ((sz > UBI_EC_HDR_SIZE) &&
+		(!memcmp((void *)data, UBI_MAGIC, UBI_MAGIC_SIZE))) {
 		if (flash_ubi_img(ptn, data, sz)) {
 			fastboot_fail("flash write failure");
 			return;