ide: add port and host iterators

Add ide_port_for_each_dev() / ide_host_for_each_port() iterators
and update IDE code to use them.

While at it:
- s/unit/i/ variable in ide_port_wait_ready(), ide_probe_port(),
  ide_port_tune_devices(), ide_port_init_devices_data(), do_reset1(),
  ide_acpi_set_state() and scc_dma_end()
- s/d/i/ variable in ide_proc_port_register_devices()

There should be no functional changes caused by this patch.

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

drivers/ide/ide-proc.c

@@ -593,14 +593,13 @@ EXPORT_SYMBOL(ide_proc_unregister_driver);
 
 void ide_proc_port_register_devices(ide_hwif_t *hwif)
 {
-	int	d;
 	struct proc_dir_entry *ent;
 	struct proc_dir_entry *parent = hwif->proc;
+	ide_drive_t *drive;
 	char name[64];
+	int i;
 
-	for (d = 0; d < MAX_DRIVES; d++) {
-		ide_drive_t *drive = hwif->devices[d];
-
+	ide_port_for_each_dev(i, drive, hwif) {
 		if ((drive->dev_flags & IDE_DFLAG_PRESENT) == 0 || drive->proc)
 			continue;