Btrfs: The file argument for fsync() is never null

The "file" argument for fsync is never null so we can remove this check.

What drew my attention here is that 7ea80859: "drop unused dentry
argument to ->fsync" introduced an unconditional dereference at the
start of the function and that generated a smatch warning.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/file.c

@@ -1139,7 +1139,7 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
 	/*
 	 * ok we haven't committed the transaction yet, lets do a commit
 	 */
-	if (file && file->private_data)
+	if (file->private_data)
 		btrfs_ioctl_trans_end(file);
 
 	trans = btrfs_start_transaction(root, 0);