btrfs: return real error from read_alloc_one_name() in drop_one_dir_item()

btrfs: return real error from read_alloc_one_name() in drop_one_dir_item()

If read_alloc_one_name() we explicitly return -ENOMEM and currently that
is fine since it's the only error read_alloc_one_name() can return for
now. However this is fragile and not future proof, so return instead what
read_alloc_one_name() returned.

Reviewed-by: Boris Burkov <boris@bur.io>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>