ide: remove "paranoia" checks for hwgroup->busy

Remove "paranoia" checks for hwgroup->busy from ide_timer_expiry()
and ide_intr().  This is a preparation for future changes.

Cc: Michael Schmitz <schmitz@biophys.uni-duesseldorf.de>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Elias Oltmanns <eo@nebensachen.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>