pata_optidma: rework for cable detect and to remove post_set_mode()

A lot of noise because I had to rename the optidma_set_mode() method to
avoid confusion with the new ->set_mode() method that was added. Cable
detect side is pretty trivial.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>