fs: fat: set start cluster for root directory

When iterating over a child directory we set itr->start_clust.
Do the same when over the root directory.

When looking for deleted directory entries or existing short names we will
have to iterate over directories a second and third time. With this patch
we do not need any special logic for the root directory.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/fs/fat/fat.c b/fs/fat/fat.c
index 674236d..5a418cf 100644
--- a/fs/fat/fat.c
+++ b/fs/fat/fat.c
@@ -734,7 +734,7 @@
 		return -ENXIO;
 
 	itr->fsdata = fsdata;
-	itr->start_clust = 0;
+	itr->start_clust = fsdata->root_cluster;
 	itr->clust = fsdata->root_cluster;
 	itr->next_clust = fsdata->root_cluster;
 	itr->dent = NULL;
@@ -778,6 +778,7 @@
 	} else {
 		itr->clust = parent->fsdata->root_cluster;
 		itr->next_clust = parent->fsdata->root_cluster;
+		itr->start_clust = parent->fsdata->root_cluster;
 		itr->is_root = 1;
 	}
 	itr->dent = NULL;
@@ -1067,6 +1068,7 @@
 			/* point back to itself */
 			itr->clust = itr->fsdata->root_cluster;
 			itr->next_clust = itr->fsdata->root_cluster;
+			itr->start_clust = itr->fsdata->root_cluster;
 			itr->dent = NULL;
 			itr->remaining = 0;
 			itr->last_cluster = 0;