ide-tape: remove idetape_pipeline_size()

The computation of the block offset of the the tape position (MTIOCPOS,
MTIOCGET) is not influenced by the stages queued in the pipeline anymore but by
the size of the current buffer which is going to be sent to the drive.

[bart: resurrect deleted idetape_wait_for_pipeline() call]

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