btrfs: heuristic: open code get_num callback of radix sort

The callback is trivial and we don't need the abstraction for our
purposes. Let's open code it and also make the array types explicit.

Reviewed-by: Timofey Titovets <nefelim4ag@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>
1 file changed