UBIFS: switch to I/O helpers

Switch the rest of direct UBI calls to UBIFS helper functions.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
diff --git a/fs/ubifs/sb.c b/fs/ubifs/sb.c
index 701dccc..93d938a 100644
--- a/fs/ubifs/sb.c
+++ b/fs/ubifs/sb.c
@@ -674,7 +674,7 @@
 
 	if (len == 0) {
 		dbg_mnt("unmap empty LEB %d", lnum);
-		return ubi_leb_unmap(c->ubi, lnum);
+		return ubifs_leb_unmap(c, lnum);
 	}
 
 	dbg_mnt("fixup LEB %d, data len %d", lnum, len);
@@ -682,7 +682,7 @@
 	if (err)
 		return err;
 
-	return ubi_leb_change(c->ubi, lnum, c->sbuf, len, UBI_UNKNOWN);
+	return ubifs_leb_change(c, lnum, c->sbuf, len, UBI_UNKNOWN);
 }
 
 /**