ide: make ide_unregister() take 'ide_hwif_t *' as an argument (take 2)

* Make ide_unregister() take 'ide_hwif_t *hwif' instead of 'unsigned int
  index' (hwif->index) as an argument and update all users accordingly.

While at it:

* Remove unnecessary checks for hwif != NULL from ide-pnp.c::idepnp_remove()
  and delkin_cb.c::delkin_cb_remove().

* Remove needless hwif->chipset assignment from scc_pata.c::scc_remove().

v2:
* Fixup ide_unregister() documentation.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/include/linux/ide.h b/include/linux/ide.h
index a1f290d..f4c7ec2 100644
--- a/include/linux/ide.h
+++ b/include/linux/ide.h
@@ -1210,7 +1210,7 @@
 #endif
 
 void ide_remove_port_from_hwgroup(ide_hwif_t *);
-void ide_unregister(unsigned int);
+void ide_unregister(ide_hwif_t *);
 
 void ide_register_region(struct gendisk *);
 void ide_unregister_region(struct gendisk *);