Remove bunch of unnecessary code from encode_transform_unit.
Remove bunch of unnecessary code from encode_transform_unit.

- Really, it's useless. Selecting scan order isn't this hard.

- Checked from HM that ctx_idx doesn't have anything to do with contexts.

ultravideo/kvazaar,lu-zero/kvazaar,lu-zero/kvazaar,lu-zero/kvazaar,ultravideo/kvazaar,lu-zero/kvazaar,ultravideo/kvazaar,ultravideo/kvazaar,ultravideo/kvazaar