ide: remove [ata_]select_t

* Use 'drive->dn & 1' in ide_init_disk().

* remove [ata_]select_t.

While at it:

* Use ATA_DEVICE_OBS define in ide_port_init_devices_data().

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