ide: add struct ide_host (take 3)

* Add struct ide_host which keeps pointers to host's ports.

* Add ide_host_alloc[_all]() and ide_host_remove() helpers.

* Pass 'struct ide_host *host' instead of 'u8 *idx' to
  ide_device_add[_all]() and rename it to ide_host_register[_all]().

* Convert host drivers and core code to use struct ide_host.

* Remove no longer needed ide_find_port().

* Make ide_find_port_slot() static.

* Unexport ide_unregister().

v2:
* Add missing 'struct ide_host *host' to macide.c.

v3:
* Fix build problem in pmac.c (s/ide_alloc_host/ide_host_alloc/)
  (Noticed by Stephen Rothwell).

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/ppc/pmac.c b/drivers/ide/ppc/pmac.c
index ee557d1..ecd2f28 100644
--- a/drivers/ide/ppc/pmac.c
+++ b/drivers/ide/ppc/pmac.c
@@ -1039,9 +1039,9 @@
 {
 	struct device_node *np = pmif->node;
 	const int *bidp;
+	struct ide_host *host;
 	ide_hwif_t *hwif;
 	hw_regs_t *hws[] = { hw, NULL, NULL, NULL };
-	u8 idx[4] = { 0xff, 0xff, 0xff, 0xff };
 	struct ide_port_info d = pmac_port_info;
 
 	pmif->broken_dma = pmif->broken_dma_warn = 0;
@@ -1118,13 +1118,13 @@
 			 pmif->mdev ? "macio" : "PCI", pmif->aapl_bus_id,
 			 pmif->mediabay ? " (mediabay)" : "", hw->irq);
 
-	hwif = ide_find_port_slot(&d);
-	if (hwif == NULL)
+	host = ide_host_alloc(&d, hws);
+	if (host == NULL)
 		return -ENOENT;
 
-	idx[0] = hwif->index;
+	ide_host_register(host, &d, hws);
 
-	ide_device_add(idx, &d, hws);
+	hwif = host->ports[0];
 
 	return 0;
 }