When Patrick removed ide_notify_reboot() in 2.5.42, he didn't notice
that it meant that IDE no longer had any shutdown() functionality.

So we did the right thing on suspend, but not on shutdown.

ide_notify_reboot() was only doing STANDBY on shutdown (because FLUSH
'doesn't work' in 2.4 too) but it worked okay and we still should do STANDBY
on shutdown because some broken disks flush their caches.

Thus just calls bus->suspend() (FLUSH+STANDBY) at shutdown time.  We can
add some safety delay later - 2.4 doesn't have any.