ANDROID: fixup task_struct to avoid ABI breakage

Reuse task_struct.worker_private to store task_dma_buf_info pointer and
avoid adding new task_struct members that would lead to ABI breakage.
For kthreads we add task_dma_buf_info member to struct kthread to store
dmabuf accounting information. io_workers do not map dmabufs, so we
do not store dmabuf accounting information for them.

Bug: 424648392
Bug: 434753952
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
(cherry picked from https://android-review.googlesource.com/q/commit:4efa97345de62a0b8a8e94922448ca2952f6bf56)
Merged-In: I90bf6762db62f36a2ef80e345bfa811016cdff8b
Change-Id: I90bf6762db62f36a2ef80e345bfa811016cdff8b