ide: remove ide_find_best_pio_mode()

* Add ->host_flags to ide_hwif_t to store ide_pci_device_t.host_flags,
  assign it in setup-pci.c:ide_pci_setup_ports().

* Add IDE_HFLAG_PIO_NO_{BLACKLIST,DOWNGRADE} to ide_pci_device_t.host_flags
  and teach ide_get_best_pio_mode() about them.  Also remove needless
  !drive->id check while at it (drive->id is always present).

* Convert amd74xx, via82cxxx and ide-timing.h to use ide_get_best_pio_mode()
  and then remove no longer needed ide_find_best_pio_mode().

There should be no functionality changes caused by this patch.

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