ide: print message on error in ide_find_port_slot()

* Add DRV_NAME define to ide-h8300.c.

* Fix ide-h8300.c, swarm.c and sgiioc4.c to set .name field in
  struct ide_port_info to DRV_NAME, then convert these host drivers
  to use ide_find_port_slot() instead of ide_find_port().

* Print message on error in ide_find_port_slot().

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>