The appropriate functionality of the callback is established through querying
the ATAPI packet command in pc->c[0].

While at it:
- add uptodate variable + leave just one idetape_end_request() call
- don't use HWGROUP() macro

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