ide: ide_id_to_hd_driveid() -> ata_id_to_hd_driveid()

Rename ide_id_to_hd_driveid() to ata_id_to_hd_driveid()
and move it to <linux/ata.h>.

Cc: Jeff Garzik <jgarzik@pobox.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>