ext4: flag as supporting buffered async reads

ext4 uses generic_file_read_iter(), which already supports this.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 0d62425..9f7d9bf 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -826,7 +826,7 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
 			return ret;
 	}
 
-	filp->f_mode |= FMODE_NOWAIT;
+	filp->f_mode |= FMODE_NOWAIT | FMODE_BUF_RASYNC;
 	return dquot_file_open(inode, filp);
 }