Revert "Ensure that the decoder is init once only."

This reverts commit 6d637d4801095acfe5b6a7e56f446aa2e4602bfa.

It caused Heap corruption when opening vc-1 files which has an mpeg context and therefore needs to init twice. We cannot NULL it, because it was still in use. Let's do it as we do for all the other hw decoders.