* Add PIO 4 support.
While at it:
* Use a single struct ide_port_info instance for OPTi621 and OPTi621X.
Based on a bugreport from Juergen Kosel & inspired by pata_opti.c code.
Tested-by: Juergen Kosel <juergen.kosel@gmx.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>