ide: add ide_device_{get,put}() helpers

* Add 'struct ide_host *host' field to ide_hwif_t and set it
  in ide_host_alloc_all().

* Add ide_device_{get,put}() helpers loosely based on SCSI's
  scsi_device_{get,put}() ones.

* Convert IDE device drivers to use ide_device_{get,put}().

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

drivers/ide/ide-probe.c

@@ -1595,6 +1595,8 @@ struct ide_host *ide_host_alloc_all(const struct ide_port_info *d,
 
 		ide_init_port_data(hwif, idx);
 
+		hwif->host = host;
+
 		host->ports[i] = hwif;
 		host->n_ports++;
 	}