ide: turn set_irq() method into write_devctl() method

Turn set_irq() method with its software reset hack into write_devctl() method
(for just writing a value into the device control register) at last...

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>