ide-tape: struct idetape_tape_t: remove unused members

- last_frame_position: only being written to once
- firmware_revision, product_id, vendor_id: used once, remove from struct
  idetape_tape_t and deal with them locally
- firmware_revision_num: only written to once
- tape_still_time_begin: completely unused
- tape_still_time: never written to; remove corresponding code chunk
- uncontrolled_last_pipeline_head: only once written to
- blocks_in_buffer: only written to

Signed-off-by: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>