btrfs: use inode already stored in local variable at btrfs_rmdir()

There's no need to call d_inode(dentry) when calling btrfs_unlink_inode()
since we have already stored that in a local inode variable. So just use
the local variable to make the code less verbose.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: fdmanana

fs/btrfs/inode.c

@@ -4759,8 +4759,7 @@ static int btrfs_rmdir(struct inode *dir, struct dentry *dentry)
 		goto out;
 
 	/* now the directory is empty */
-	ret = btrfs_unlink_inode(trans, BTRFS_I(dir), BTRFS_I(d_inode(dentry)),
-				 &fname.disk_name);
+	ret = btrfs_unlink_inode(trans, BTRFS_I(dir), BTRFS_I(inode), &fname.disk_name);
 	if (!ret)
 		btrfs_i_size_write(BTRFS_I(inode), 0);
 out: