ide: ide_find_best_pio_mode() fixes (take 2)

* Check IORDY bit for PIO modes > 2.

* Some devices claim maximum PIO mode > 2 in id->tPIO, they were punished too
  severly for this by being limited to PIO_SLOW.  Limit them to PIO2 instead.

v2:
* Fix PIO number being returned incorrectly instead of PIO mode
  (Noticed by Sergei).

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