pata_hpt{37x,3x2n}: add debounce delay to cable detection methods

Alan Cox reported that cable detection sometimes works unreliably
for HPT3xxN and that the issue is fixed by adding debounce delay
as used by the vendor driver.

Sergei Shtylyov also noticed that debounce delay is needed for all
HPT37x and HPT3xxN chipsets according to vendor drivers.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>