Stop abusing ide_lock lock by switching to a private locking.

Fixes same issue as fixed by Alan Cox in atiixp host driver with
commit 6c5f8cc3.
Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>