vfs: use helpers for calling f_op->{read,write}_iter()

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
diff --git a/fs/splice.c b/fs/splice.c
index 873d831..6518f05 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -306,7 +306,7 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 	idx = to.idx;
 	init_sync_kiocb(&kiocb, in);
 	kiocb.ki_pos = *ppos;
-	ret = in->f_op->read_iter(&kiocb, &to);
+	ret = call_read_iter(in, &kiocb, &to);
 	if (ret > 0) {
 		*ppos = kiocb.ki_pos;
 		file_accessed(in);