ide: remove ide_dma_iobase()

* ide_mapped_mmio_dma() and ide_iomio_dma() are called only by
  ide_dma_iobase() so inline them there.

* ide_dma_iobase() is called only by ide_setup_dma() so inline
  it there.

* Setup hwif->extra_base also if hwif->mmio flag is set.

There should be no functional changes casued by this patch.

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