- Remove the specific CONFIG_IDEDMA_PCI_WIP in favor of using the generic
   CONFIG_EXPERIMENTAL tag. (Pointed out by Vojtech Pavlik).

- Change the signature of the IRQ handler to take the request directly as a
   parameter. This doesn't blow the code up but makes it much more obvious and
   finally it's reducing the number of side effects of the hwgroup->rq field.

- A second sharp look after the above change allowed us to remove the wrq field
   from the hwgroup struct. It's just not used at all.

- Change the signature of the end_request member of struct ata_operations to
   take the request as a second argument. Similar for __ide_end_request()
   and ide_end_request().

- Remove BUG_ON() items just before ide_set_handler(). The check in
   ide_set_handler is clever enough now.

- Remove the rq subfield from ide-scsi packet structure. We have now the
   request context always in place. Same for floppy.

- Let the timer expiry function take the request as a direct argument.

Yes I know those changes are extensive. But they are a necessary step
in between for the following purposes:

- Consolidate the whole ATA/ATAPI stuff on passing a single unified request
   handling object. Because after eliminating those side effects it's far easier
   to see what's passed where.

- Minimizing the amount of side effects in the overall code. That's a good
   thing anyway and it *doesn't* cost us neither performance nor space, since
   the stack depths are small anyway here.

- Minimizing the usage of hwgroup - which should go away if possible.