ide-floppy: do not complete rq's prematurely

... and access them afterwards. Simplify rq completing code while at it.

Spotted-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>