The check length of system image path is incorrect

Change-Id: I48042c0acb642e417105986010915ec0a78437b9
diff --git a/yaffs2/utils/mkyaffs2image.c b/yaffs2/utils/mkyaffs2image.c
index 250cf11..820a238 100644
--- a/yaffs2/utils/mkyaffs2image.c
+++ b/yaffs2/utils/mkyaffs2image.c
@@ -511,7 +511,7 @@
         
         if((len >= 4) && (!strcmp(argv[1] + len - 4, "data"))) {
             source_path_len = len - 4;
-        } else if((len >= 7) && (!strcmp(argv[1] + len - 6, "system"))) {
+        } else if((len >= 6) && (!strcmp(argv[1] + len - 6, "system"))) {
             source_path_len = len - 6;
         } else {            
             fprintf(stderr,"Fixstats (-f) option requested but filesystem is not data or android!\n");