btrfs: remove root argument from btrfs_unlink_inode()

btrfs: remove root argument from btrfs_unlink_inode()

[ Upstream commit 4467af8809299c12529b5c21481c1d44a3b209f9 ]

The root argument passed to btrfs_unlink_inode() and its callee,
__btrfs_unlink_inode(), always matches the root of the given directory and
the given inode. So remove the argument and make __btrfs_unlink_inode()
use the root of the directory.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>