amd74xx/via82cxxx: don't initialize drive->dn

drive->dn is initialized by ide-probe.c::probe_hwif() so no need to do it
in ->init_hwif method.

Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>