ide-tape: struct idetape_tape_t: shorten member names v2

Shorten some member names not too aggressively since this driver might be gone
anyway soon.

Bart:
- minor fixes

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