ide: make ide_get_best_pio_mode() print info if overriding PIO mode

* Print info about overriding PIO mode in ide_get_best_pio_mode().

* Remove info about overriding PIO mode from cmd64{0,x} host drivers.

* Remove no longer needed ide_pio_data_t.overridden field.

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